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Includes bibliographical references (p. 434-437) and index

Core PHP Programming, Second Edition is the first complete, practical guide to PHP 4 for experienced Web developers. Fully updated to reflect PHP 4.0's breakthrough features and performance, it covers every technique you need to build robust, fast Web applications. Leading PHP developer Leon Atkinson starts with a high-level overview of PHP: how it evolved, and how it appears to the developer. Next, Atkinson reviews the key building blocks of PHP scripts, including variables, operators, and expressions; conditional branches and loops. Review every PHP function, including I/O, data, and math functions; time, date, configuration, database, graphics, and network functions. Core PHP Programming, Second Edition also contains detailed coverage of effective program design and debugging. For all Web developers and system administrators.

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Programacion websocket java

A learning environment which increases the desire and efforts of students to attain learning goals leads to greater motivation and success. This study examines the negative and positive opinions of students regarding the effectiveness of the learning process and students' success in a computer programming course in which face-to-face and web-based e-learning methods were blended. The study, for which the case study method is used, was carried out over a 12 week period with the participation of 44 students. A data collection tool consisting of open-ended questions was applied to the participants at the end of the process. The replies given by the participants to the data collection tool were analyzed using qualitative analysis techniques. At the end of the research, the evaluation and satisfaction scores of the students regarding the web-based blended learning environment were found to be positive to a high degree. The positive opinions of the students were focused particularly around four themes, namely "facilitating learning through the learning environment"; "providing interaction opportunities"; "encouraging research," "video support for the course." Negative opinions were gathered around the themes of "lack of sufficient teaching time," "experiencing technical failures," "course badly scheduled" and "comprehensiveness of the course content."

The Tawny-OWL library provides a fully-programmatic environment for ontology building; it enables the use of a rich set of tools for ontology development, by recasting development as a form of programming. It is built in Clojure - a modern Lisp dialect, and is backed by the OWL API. Used simply, it has a similar syntax to OWL Manchester syntax, but it provides arbitrary extensibility and abstraction. It builds on existing facilities for Clojure, which provides a rich and modern programming tool chain, for versioning, distributed development, build, testing and continuous integration. In this paper, we describe the library, this environment and the its potential implications for the ontology development process.

Welcome to the Web, from Khan Academy

Welcome to the Web, from Khan Academy

Welcome to the Web, from Khan Academy

We extend the Jolie programming language to capture the native modelling of process-aware web information systems, i.e., web information systems based upon the execution of business processes. Our main contribution is to offer a unifying approach for the programming of distributed architectures on the web, which can capture web servers, stateful process execution, and the composition of services via mediation. We discuss applications of this approach through a series of examples that cover, e.g., static content serving, multiparty sessions, and the evolution of web systems. Finally, we present a performance evaluation that includes a comparison of Jolie-based web systems to other frameworks and a measurement of its scalability.

by Krzysztof Cieslak At: FOSDEM 2019 https://video.fosdem.org/2019/K.3.201/dotnet_fsharp_reinventing_mvc.webm The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#. The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern Room: K.3.201 Scheduled start: 2019-02-02 16:30:00+01 Source: https://www.youtube.com/watch?v=BhIFV4m0jEs Uploader: FOSDEM

by Krzysztof Cieslak At: FOSDEM 2019 https://video.fosdem.org/2019/K.3.201/dotnet_fsharp_reinventing_mvc.webm The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#. The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern Room: K.3.201 Scheduled start: 2019-02-02 16:30:00+01 Source: https://www.youtube.com/watch?v=BhIFV4m0jEs Uploader: FOSDEM

by Krzysztof Cieslak At: FOSDEM 2019 https://video.fosdem.org/2019/K.3.201/dotnet_fsharp_reinventing_mvc.webm The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#. The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern Room: K.3.201 Scheduled start: 2019-02-02 16:30:00+01 Source: https://www.youtube.com/watch?v=BhIFV4m0jEs Uploader: FOSDEM

by Krzysztof Cieslak At: FOSDEM 2019 https://video.fosdem.org/2019/K.3.201/dotnet_fsharp_reinventing_mvc.webm The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#. The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern Room: K.3.201 Scheduled start: 2019-02-02 16:30:00+01 Source: https://www.youtube.com/watch?v=BhIFV4m0jEs Uploader: FOSDEM

by Krzysztof Cieslak At: FOSDEM 2019 https://video.fosdem.org/2019/K.3.201/dotnet_fsharp_reinventing_mvc.webm The MVC pattern has been one of the most important architectural patterns for server-side web development - it has been implemented and popularized by frameworks like Ruby On Rail or ASP.NET MVC. However, this pattern was traditionally coupled with object-oriented programming. In the talk, I will show how to reinvent MVC pattern, and structure your web application in a functional language - F#. The talk will cover some brief introduction to F# - modern functional programming language running on .Net platform, show how to model MVC layers using functional composition, and at the end show some examples of applying MVC pattern with Saturn - opinionated, web development framework for F# which implements the server-side, functional MVC pattern Room: K.3.201 Scheduled start: 2019-02-02 16:30:00+01 Source: https://www.youtube.com/watch?v=BhIFV4m0jEs Uploader: FOSDEM

In addition to learning technical aspects of website creation, students must connect different knowledge, think critically, seek more information, and approach their work from various perspectives. These requirements, or specified competencies, can be developed through providing and receiving peer feedback, which is confirmed as an efficient learning strategy in various empirical studies on different subjects. The aim of this research is to investigate the impact of peer feedback on students’ achievements in the Web Programming Course. We conducted a quantitative study with two groups of students. Students from the experimental group participated in online giving and receiving peer feedback regarding students’ assignments, while students from the control group did not have this opportunity. For evaluating students’ work, we used rubrics. The results indicate that students, through analyzing their peers’ work, providing qualitative assessments, reflecting on their work in line with received comments, and making necessary corrections, create content that surpasses the quality of websites created by their peers who did not have the opportunity to participate in peer feedback activities. Since students extensively analyzed their work after receiving comments and suggestions, made specific corrections, and consequently improved their projects, organizing peer feedback activities in programming courses, especially web programming, should be given more attention. Enable Ginger Cannot connect to Ginger Check your internet connection or reload the browserDisable GingerRephraseRephrase with Ginger (Ctrl+Alt+E) Edit in Ginger Ginger is checking your text for mistakes... Disable Ginger in this text fieldDisable Ginger on this website×

In addition to learning technical aspects of website creation, students must connect different knowledge, think critically, seek more information, and approach their work from various perspectives. These requirements, or specified competencies, can be developed through providing and receiving peer feedback, which is confirmed as an efficient learning strategy in various empirical studies on different subjects. The aim of this research is to investigate the impact of peer feedback on students’ achievements in the Web Programming Course. We conducted a quantitative study with two groups of students. Students from the experimental group participated in online giving and receiving peer feedback regarding students’ assignments, while students from the control group did not have this opportunity. For evaluating students’ work, we used rubrics. The results indicate that students, through analyzing their peers’ work, providing qualitative assessments, reflecting on their work in line with received comments, and making necessary corrections, create content that surpasses the quality of websites created by their peers who did not have the opportunity to participate in peer feedback activities. Since students extensively analyzed their work after receiving comments and suggestions, made specific corrections, and consequently improved their projects, organizing peer feedback activities in programming courses, especially web programming, should be given more attention. Enable Ginger Cannot connect to Ginger Check your internet connection or reload the browserDisable GingerRephraseRephrase with Ginger (Ctrl+Alt+E) Edit in Ginger Ginger is checking your text for mistakes... Disable Ginger in this text fieldDisable Ginger on this website×

xxii, 741 p. : 23 cm

web programming dumped with WikiTeam tools.

web programming dumped with WikiTeam tools.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

The Chromium Projects Home Chromium ChromiumOS Quick links Report bugs Discuss Other sites Chromium Blog Google Chrome Extensions Except as otherwise  noted , the content of this page is licensed under a  Creative Commons Attribution 2.5 license , and examples are licensed under the  BSD License . Privacy Edit this page For Developers  >  How-Tos  > Debugging Chromium on Windows First see  get the code  for checkout and build instructions. Getting started You can use Visual Studio's built-in debugger or  WinDBG  to debug Chromium. You don't need to use the IDE to build in order to use the debugger: autoninja is used to build Chromium and most developers invoke it from a command prompt, and then open the IDE for debugging as necessary. To start debugging an already-built executable with Visual Studio just launch Visual Studio (2019 or higher) and select File-> Open-> Project/Solution (Ctrl+Shift+O) and select the executable of interest. This will create a solution with that executable as the 'project'. You can then launch the debugger with F5 or F11 or from the Debug menu. If you right-click on the executable in Solution Explorer and select properties then you can edit things such as the executable path, command-line arguments, and working directory. You can add additional executables to the solution by using File-> Add-> Existing Project and selecting another already-built executable. You can select which one to debug by right-clicking on one of them in Solution Explorer and selecting Set as Startup Project. When your solution file is customized to your taste you can save it to a directory such as out\solutions. Saving it there helps ensure that relative paths to source files, printed from build commands, will correctly identify the source files. The Tools menu can be used to add commands to do things like invoke autoninja to build Chrome, compile the selected source file, or other things. Visual Studio 2017 is not recommended for debugging of Chromium - use a newer version for best performance and stability. symbol_level=2  is the default on Windows and gives full debugging information with types, locals, globals, function names, and source/line information.  symbol_level=1  creates smaller PDBs with just function names, and source/line information - source-level debugging is still supported (new from June 2019), but local variables and type information are missing.  symbol_level=0  gives extremely limited debugging abilities, mostly just viewing call stacks when Chromium crashes. Browsing source code If you use a solution file generated by gn ( gn gen --ide=vs ) then Intellisense may help you navigate the code. If this doesn't work or if you use a solution created as above then you may want to install  VsChromium  to help navigate the code, as well as using  https://source.chromium.org . Profiles It's a good idea to use a different Chrome profile for your debugging. If you are debugging Google Chrome branded builds, or use a Chromium build as your primary browser, the profiles can collide so you can't run both at once, and your stable browser might see profile versions from the future (Google Chrome and Chromium use different profile directories by default so won't collide). Use the command-line option: --user-data-dir =C:\tmp\my_debug_profile (replace the path as necessary) Using the IDE, go to the  Debugging  tab of the properties of the chrome project, and set the  Command Arguments. Chrome debug log Enable Chrome debug logging to a file by passing  --enable-logging --v=1  command-line flags at startup. Debug builds place the  chrome_debug.log  file in the  out\Debug  directory. Release builds place the file in the top level of the user data Chromium app directory, which is OS-version-dependent. For more information, see  logging  and  user data directory  details. Symbol server If you are debugging official Google Chrome release builds, use the symbol server: https://chromium-browser-symsrv.commondatastorage.googleapis.com In Visual Studio, this goes in  Tools > Options  under  Debugging > Symbols . You should set up a local cache in a empty directory on your computer. In windbg you can add this to your symbol server search path with the command below, where C:\symbols is a local cache directory: .sympath+ SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Alternately, You can set the _NT_SYMBOL_PATH environment variable to include both the Microsoft and Google symbol servers - VS, windbg, and other tools should both respect this environment variable: _NT_SYMBOL_PATH =SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols ;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com Note that symbol servers will let the debuggers download both the PE files (DLLs and EXEs) and the PDB files. Chrome often loads third party libraries and partial symbols for some of these are also public. For example: AMD : https://download.amd.com/dir/bin Nvidia : https://driver-symbols.nvidia.com/ Intel : https://software.intel.com/sites/downloads/symbols/ For example, for completeness, the following symbol server environment variable will resolve all of the above sources - but this is more than is normally needed: _NT_SYMBOL_PATH=SRV\*C:\symbols\*https://msdl.microsoft.com/download/symbols;SRV\*C:\symbols\*https://chromium-browser-symsrv.commondatastorage.googleapis.com;SRV\*C:\symbols\*https://download.amd.com/dir/bin;SRV\*C:\symbols\*https://driver-symbols.nvidia.com/;SRV\*C:\symbols\*https://software.intel.com/sites/downloads/symbols/ Source indexing You should set up source indexing in your debugger ( .srcfix  in windbg, Tools-> Options-> Debugging-> General->  Enable source server support  in Visual Studio) so that the correct source files will automatically be downloaded based on information in the downloaded symbols. Additionally, you must have  python  in your  path  in order for the  command that fetches source files  to succeed; launching the debugger from the same environment as where you build Chromium is an easy way to ensure it's present. This is highly recommended when debugging released Google Chrome builds or looking at crash dumps. Having the correct version of the source files automatically show up saves significant time so you should definitely set this. Multi-process issues Chromium can be challenging to debug because of its  multi-process architecture . When you select  Run  in the debugger, only the main browser process will be debugged. The code that actually renders web pages (the Renderer) and the plugins will be in separate processes that's not (yet!) being debugged. The  ProcessExplorer  tool has a process tree view where you can see how these processes are related. You can also get the process IDs associated with each tab from the Chrome Task Manager (right-click on an empty area of the window title bar to open). Automatically attach to child processes There are two Visual Studio extensions that enable the debugger to automatically attach to all Chrome processes, so you can debug all of Chrome at once. Microsoft's  Child Process Debugging Power Tool  is a standalone extension for this, and  VsChromium  is another option that bundles many other additional features. In addition to installing one of these extensions, you  must  run Visual Studio as Administrator, or it will silently fail to attach to some of Chrome's child processes. Single-process mode One way to debug issues is to run Chromium in single-process mode. This will allow you to see the entire state of the program without extra work (although it will still have many threads). To use single-process mode, add the command-line flag --single-process This approach isn't perfect because some problems won't manifest themselves in this mode and some features don't work and worker threads are still spawned into new processes. Manually attaching to a child process You can attach to the running child processes with the debugger. Select  Tools > Attach to Process  and click the  chrome.exe  process you want to attach to. Before attaching, make sure you have selected only Native code when attaching to the process This is done by clicking Select... in the Attach to Process window and only checking Native. If you forget this, it may attempt to attach in "WebKit" mode to debug JavaScript, and you'll get an error message "An operation is not legal in the current state." You can now debug the two processes as if they were one. When you are debugging multiple processes, open the  Debug > Windows > Processes  window to switch between them. Sometimes you are debugging something that only happens on startup, and want to see the child process as soon as it starts. Use: --renderer-startup-dialog --no-sandbox You have to disable the sandbox or the dialog box will be prohibited from showing. When the dialog appears, visit Tools > Attach to Process and attach to the process showing the Renderer startup dialog. Now you're debugging in the renderer and can continue execution by pressing OK in the dialog. Startup dialogs also exist for other child process types:  --gpu-startup-dialog ,  --ppapi-startup-dialog ,  --utility-startup-dialog ,  --plugin-startup-dialog  (for NPAPI). For utilities, you can add a service type  --utility-startup-dialog=data_decoder.mojom.DataDecoderService . You can also try  the vs-chromium plug-in  to attach to the right processes. Semi-automatically attaching the debugger to child processes The following flags cause child processes to wait for 60 seconds in a busy loop for a debugger to attach to the process. Once either condition is true, it continues on; no exception is thrown. --wait-for-debugger-children [=filter] The filter, if provided, will fire only if it matches the  --type  parameter to the process. Values include  renderer ,  plugin  (for NPAPI),  ppapi ,  gpu-process , and  utility . When using this option, it may be helpful to limit the number of renderer processes spawned, using: --renderer-process-limit = 1 Image File Execution Options Using Image File Execution Options (IFEO) will not work because CreateProcess() returns the handle to the debugger process instead of the intended child process. There are also issues with the sandbox. Time travel debugging You can do  time travel debugging using WinDbg Preview  (must be installed from the Microsoft Store). This lets you execute a program forward and backwards. After capturing a trace, you can set breakpoints and step through code as normal, but also provides 'backwards' commands (g-, t-, p-) so that you can go back and forth through the execution. It is especially useful to set data breakpoints ( ba command ) and reverse continuing, so you can see when a certain variable was last changed to its current value. Chromium specifics: The type of injection the time travel tracer needs to perform is incompatible with the Chromium sandbox. In order to record a trace, you'll need to run with  --no-sandbox . Chromium cannot run elevated with Administrator privileges, so the "Launch executable (advance)" option won't work, you'll need to attach after the process has already launched via the checkbox in the bottom right. If you need to record startup-like things, you'll have to use --{browser,gpu,renderer,utility}-startup-dialog, then attach (and hope the relevant code hasn't executed before that point). JsDbg -- data structure visualization You can install  JsDbg as a plugin for WinDbg or Visual Studio . It interactively lets you look at data structures (such as the DOM tree, Accessibility tree, layout object tree, and others) in a web browser as you debug. See the  JsDbg site  for some screen shots and usage examples. This also works when examining memory dumps (though not minidumps), and also works together with time travel debugging. Visual Studio hints Debug visualizers Chrome's custom debug visualizers should be added to the pdb files and automatically picked up by Visual Studio. The definitions are in  //tools/win/DebugVisualizers  if you need to modify them (the BUILD.gn file there has additional instructions). Don't step into trivial functions The debugger can be configured to automatically not step into functions based on regular expression. Edit  default.natstepfilter  in the following directory: For Visual Studio 2015:  C:\Program Files (x86)\Microsoft Visual Studio 14.0\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2015\Visualizers  (for the current user only) For Visual Studio 2017 Pro:  C:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\Common7\Packages\Debugger\Visualizers  (for all users) or  %USERPROFILE%\My Documents\Visual Studio 2017\Visualizers  (for the current user only) Add regular expressions of functions to not step into. Remember to regex-escape  and  XML-escape them, e.g. < for < and \. for a literal dot. Example: < Function > < Name > operator new </ Name > < Action > NoStepInto </ Action > </ Function > < Function > < Name > operator delete </ Name > < Action > NoStepInto </ Action > </ Function > <!-- Skip everything in std --> < Function > < Name > std::.* </ Name > < Action > NoStepInto </ Action > </ Function > <!-- all methods on WebKit OwnPtr and variants, ... WTF::*Ptr<*>::* --> < Function > < Name > WTF::.*Ptr<.*>::.* </ Name > < Action > NoStepInto </ Action > </ Function > This file is read at start of a debugging session (F5), so you don't need to restart Visual Studio after changing it. More info:  Microsoft email thread V8 and Chromium V8 supports many command-line flags that are useful for debugging. V8 command-line flags can be set via the Chromium command-line flag --js-flags; for instance: chrome.exe --js-flags= "--trace_exception --heap_stats" Note that some V8 command-line flags exist only in the debug build of V8. For a list of all V8 flags try: chrome.exe --js-flags= "--help" Graphics debugging GPU Acceleration of rendering can be more easily debugged with tools. See: Graphics Debugging in Visual Studio 2013 Graphical debugging with NVIDIA NSight Debugging on another machine Sometimes it's useful to debug installation and execution on a machine other than your primary build box. To run the installer on said other machine, first build the mini_installer target on your main build machine (e.g., autoninja -C out\Debug mini_installer). Next, on the debug machine: Make the build machine's build volume available on the debug machine either by mounting it locally (e.g., Z:\) or by crafting a UNC path to it (e.g., \\builder\src) Open up a command prompt and change to a local disk Run src\tools\win\ copy-installer.bat  in the remote checkout by way of the mount (e.g., Z:\PATHTOCHECKOUT\src\...) or UNC path (e.g., \\builder\src\...). This will copy the installer, DLLs, and PDBs into your debug machine's C:\out or C:\build (depending on if you're rocking the component=shared_library build or not) Run  C:\out\Debug\mini_installer.exe  with the flags of your choice to install Chrome. This can take some time, especially on a slow machine. Watch the Task Manager and wait until mini_installer.exe exits before trying to launch Chrome (by way of the shortcut(s) created by the installer) For extra pleasure, add C:\out\Debug to your _NT_SYMBOL_PATH environment variable Consider reading the documentation at the top of copy-installer.bat to see how you can run it. It tries to be smart and copy the right things, but you may need to be explicit (e.g., "copy-installer.bat out Debug"). It is safe to re-run the script to copy only modified files (after a rebuild, for example). You can also use the zip action of the isolate scripts (tools\mb\mb.py) to package all the files for a target into a single zip file, for example: python tools\mb\mb.py zip out/Release base_unittests base_unittests. zip Finding all memory allocations It is possible to use Heap Snapshots to get call stacks on all outstanding allocations that use the OS heap. This works particularly well if heap snapshots are started as soon as the Chrome browser process is created, but before it starts running. Details can be found in  this batch file . However, with  PartitionAlloc Everywhere  most Chromium allocations no longer use the Windows heap so this will only find a subset of allocations, mostly from OS DLLs. Find memory leaks Note: as with Heap Snapshots the utility of UMDH is greatly reduced now because PartitionAlloc Everywhere has mostly replaced the Windows heap. The Windows heap manager has a really useful debug flag, where it can be asked to capture and store a stack trace with every allocation. The tool to scrape these stack traces out of processes is UMDH, which comes with  WinDbg . UMDH is great. It will capture a snapshot of the heap state as many times as you like, and it'll do it fairly quickly. You then run it again against either a single snapshot, or a pair of snapshots, at which time it'll symbolize the stack traces and aggregate usage up to unique stack traces. Turning on the user stack trace database for chrome.exe with gflags.exe makes it run unbearably slowly; however, turning on the user stack trace database on for the browser alone is just fine. While it's possible to turn on the user stack database with the "!gflag" debugging extension, it's too late to do this by the time the initial debugger breakpoint hits. The only reasonable way to do this is to Launch GFlags.exe, Enable the user stack trace database (per image below), Launch Chrome under the debugger. Set a breakpont when chrome.dll loads with "sxe ld chrome.dll". Step up, to allow Chrome.dll to initialize. Disable the stack trace database in GFlags.exe. Continue chrome, optionally detaching the debugger. GFlags.exe settings for user mode stack trace database. If you then ever suffer a browser memory leak, you can snarf a dump of the process with umdh - p :<my browser pid> > chrome-browser-leak-umdh-dump.txt which can then typically be "trivially" analyzed to find the culprit. Miscellaneous Note that by default Application Verifier only works with non-official builds of Chromium. To use Application Verifier on official builds you need to add --disable-features=RendererCodeIntegrity to avoid sandbox crashes in renderer processes. See  crbug.com/1004989  for details. See also  this page . Application Verifier  is a free tool from Microsoft (available as part of the Windows SDK) that can be used to flush out programming errors. Starting with M68 Application Verifier can be enabled for chrome.exe without needing to disable the sandbox. After adding chrome.exe to the list of applications to be stressed you need to expand the list of Basics checks and disable the  Leak  checks. You may also need to disable  Handles  and  Locks  checks depending on your graphics driver and specific Chrome version, but the eventual goal is to have Chrome run with  Handles  and  Locks  checks enabled. When bugs are found Chrome will trigger a breakpoint so running all Chrome processes under a debugger is recommended. Chrome will run much more slowly because Application Verifier puts every heap allocation on a separate page. Note that with PartitionAlloc Everywhere most Chromium allocations don't actually go through the Windows heap and are therefore unaffected by Application Verifier. You can check the undocumented 'Cuzz' checkbox in Application Verifier to get the Windows thread scheduler to add some extra randomness in order to help expose race conditions in your code. To put a breakpoint on CreateFile(), add this break point: {,,kernel32.dll}_CreateFileW@28 {,,kernel32.dll} specifies the DLL (context operator). _ prefix means extern "C". @28 postfix means _stdcall with the stack pop at the end of the function. i.e. the number of arguments in BYTES. You can use  DebugView  from SysInternals or  sawbuck  to view LOG() messages that normally go to stderr on POSIX.

Google Lighthouse Metric

Professor Brian Kernighan became widely known through co-authorship of the first book on the C programming language with Dennis Ritchie. He worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed to the development of Unix. He is also coauthor of the AWK and AMPL programming languages.

Professor Brian Kernighan became widely known through co-authorship of the first book on the C programming language with Dennis Ritchie. He worked at Bell Labs alongside Unix creators Ken Thompson and Dennis Ritchie and contributed to the development of Unix. He is also coauthor of the AWK and AMPL programming languages.

Includes bibliographical references (p. [193]-194) and index

This paper provides an analysis of old and new programming tools for development of client/server programs, particularly World Wide Web-based programs. The focus is on development of educational systems that use interactive shared workspaces to provide portable and expandable solutions. The paper begins with a short description of relevant terms. A traditional approach is presented that uses dynamic HTML (HyperText Markup Language) pages generated by CGI (Common Gateway Interface) scripts, and drawbacks of this approach are described. Next, the paper discusses an object-oriented approach to the development of client/server programs using Java, in particular, the development of distributed systems with the help of tools such as sockets, RMI (Remote Method Invocations) and CORBA (Common Object Request Broker Architecture). Traditional and new Web servers are compared. Finally, recommendations are made on which tools should be used for development of educational systems. Contains 21 references. (Author/AEF)

This paper provides an analysis of old and new programming tools for development of client/server programs, particularly World Wide Web-based programs. The focus is on development of educational systems that use interactive shared workspaces to provide portable and expandable solutions. The paper begins with a short description of relevant terms. A traditional approach is presented that uses dynamic HTML (HyperText Markup Language) pages generated by CGI (Common Gateway Interface) scripts, and drawbacks of this approach are described. Next, the paper discusses an object-oriented approach to the development of client/server programs using Java, in particular, the development of distributed systems with the help of tools such as sockets, RMI (Remote Method Invocations) and CORBA (Common Object Request Broker Architecture). Traditional and new Web servers are compared. Finally, recommendations are made on which tools should be used for development of educational systems. Contains 21 references. (Author/AEF)

This paper provides an analysis of old and new programming tools for development of client/server programs, particularly World Wide Web-based programs. The focus is on development of educational systems that use interactive shared workspaces to provide portable and expandable solutions. The paper begins with a short description of relevant terms. A traditional approach is presented that uses dynamic HTML (HyperText Markup Language) pages generated by CGI (Common Gateway Interface) scripts, and drawbacks of this approach are described. Next, the paper discusses an object-oriented approach to the development of client/server programs using Java, in particular, the development of distributed systems with the help of tools such as sockets, RMI (Remote Method Invocations) and CORBA (Common Object Request Broker Architecture). Traditional and new Web servers are compared. Finally, recommendations are made on which tools should be used for development of educational systems. Contains 21 references. (Author/AEF)

This paper provides an analysis of old and new programming tools for development of client/server programs, particularly World Wide Web-based programs. The focus is on development of educational systems that use interactive shared workspaces to provide portable and expandable solutions. The paper begins with a short description of relevant terms. A traditional approach is presented that uses dynamic HTML (HyperText Markup Language) pages generated by CGI (Common Gateway Interface) scripts, and drawbacks of this approach are described. Next, the paper discusses an object-oriented approach to the development of client/server programs using Java, in particular, the development of distributed systems with the help of tools such as sockets, RMI (Remote Method Invocations) and CORBA (Common Object Request Broker Architecture). Traditional and new Web servers are compared. Finally, recommendations are made on which tools should be used for development of educational systems. Contains 21 references. (Author/AEF)

xxiii, 378 p. : 24 cm

1Intoxicated Ghost And Other Stories

By Arlo Bates

A charming collection of short stories, dealing with ghosts, magic, and other-worldly events that even the faint of heart will enjoy.<br> 1. The Intoxicated Ghost - a woman tries to outsmart a ghost to save the family from financial ruin.<br> 2. A Problem In Portraiture - can a man's portrait influence the man he becomes?<br> 3. Knitters In The Sun - will a father's curse keep two lovers apart?<br> 4. A Comedy In Crape - the death of the town playboy causes a dispute over who is entitled to be chief mourner<br> 5. A Meeting Of The Psychical Club - who is the hooded stranger, and are his powers real?<br> 6. Tim Calligan's Grave-Money - a poor man's final sacrifice<br> 7. Miss Gaylord and Jenny - who will ultimately be George's bride, Alice or her alter-ego?<br> 8. Dr. Polnitzski - a man in a no-win situation and his resolution<br> 9. In The Virginia Room - a Southern woman visits a Confederate War Museum on the anniversary of her husband's death and meets a Northerner. Can she forgive?<br> (Summary by ppcunningham)

2Astounding Stories 14, February 1931

By Harry Bates, Charles Willard Diffin, Anthony Gilmore, Desmond Winter Hall, F. V. W. Mason and Captain S. P. Meek

This issue includes "Werewolves of War" by D. W. Hall, "The Tentacles from Below" by Anthony Gilmore, "The Black Lamp" by Captain S. P. Meek, "Phalanxes of Atlans" by F. V. W. Mason, and continues with "The Pirate Planet" by Charles W. Diffin, - Summary by Bill Boerst

3Astounding Stories 19, July 1931

By Harry Bates, Ray Cummings, A. R. Holmes, H. Thompson Rich, Nat Schachner, Jack Williamson and Arthur L. Zagat

THE DOOM FROM PLANET 4 JACK WILLIAMSON A Ray of Fire, Green, Mysterious, Stabs Through the Night to Dan on His Ship. It Leads Him to an Island of Unearthly Peril.<br> THE HANDS OF ATEN H. G. WINTER Out of the Solid Ice Craig Hews Three Long-Frozen Egyptians and Is at Once Caught Up into Amazing Adventure. (A Complete Novelette.)<br> THE DIAMOND THUNDERBOLT H. THOMPSON RICH Locked in a Rocket and Fired into Space! Such Was the Fate which Awaited Young Stoddard at the End of the Diamond Trail!<br> THE SLAVE SHIP FROM SPACE A. R. HOLMES Three Kidnapped Earthlings Show Xantra of the Tillas How "Docile" Earth Slaves Can Be.<br> THE REVOLT OF THE MACHINES NAT SCHACHNER AND ARTHUR L. ZAGAT Something in the Many-Faceted Mind of the Master Machine Spurs It to Diabolical Revolt Against the Authority of Its Human Masters.<br> THE EXILE OF TIME RAY CUMMINGS Only Near the End of the World Does Fate Catch Up with Tugh, the Cripple Who Ran Amuck Through Time. (Conclusion.)<br> THE READERS' CORNER ALL OF US A Meeting Place for Readers of Astounding Stories.

4Astounding Stories 20, August 1931

By Harry Bates, Ralph Milne Farley, Captain S. P. Meek, R. F. Starzl and Harl Vincent

This issue contains THE DANGER FROM THE DEEP by Ralph Milne Farley Marooned on the Sea-Floor, His Hoisting Cable Cut, Young Abbot Is Left at the Mercy of the Man-Sharks<br> [BROOD OF THE DARK MOON PART 1 .We are not inlcuding this as this is the last full issue available. All 4 episodes are available in our catalogue].<br> IF THE SUN DIED by R.F Starzl Tens of Millenniums After the Death of the Sun There Comes a Young Man Who Dares to Open the Frozen Gate of Subterranea.<br> THE MIDGET FROM THE ISLAND by H.G. Winter Garth Howard, Prey to Half the Animals of the Forest, Fights Valiantly to Regain His Lost Five Feet of Size. A Complete Novelette.<br> "Jazzing up the Universe" A Science Fact<br> THE MOON WEED by Harl Vincent Unwittingly the Traitor of the Earth, Van Pits Himself Against the Inexorably Tightening Web of Plant-Beasts He Has Released from the Moon.<br> THE PORT OF MISSING PLANES by Captain S.P. Meek In the Underground Caverns of the Selom, Dr. Bird Once Again Locks Wills with the Subversive Genius, Saranoff.<br> "A Classification of the Universe " A Science Fact<br> THE READERS' CORNER ALL OF US A Meeting Place for Readers of Astounding Stories.<br> " A living disembodied heart" - Summary by Annise

5On The Tree Top

By Clara Doty Bates

A collection of Nursery Rhymes retold by the author and others. - Summary by David Lawrence <br/> <br/>*Additional Proof-listening by Christine Lehman.

LibriVox volunteers bring you 19 recordings of Blood Road by Katharine Lee Bates.<br> This was the New Year's Weekly Poetry project for December 30. 2018. <br> ------<br> Katharine Lee Bates was an American writer, poet, professor, and social activist. Although she was a renowned author and professor during her lifetime, today she is primarily remembered as the author of the words to the anthem "America the Beautiful". For 25 years, she lived with her long-time friend and companion, Katharine Coman. This poem taken from 'America the beautiful and other poems' 1911. - Summary by Wikipedia

7Henry More Smith: The Mysterious Stranger

By Walter Bates

Sometime in the month of July, 1812, nearly a hundred years ago now, a well dressed, smooth spoken man, less than thirty years of age, made his appearance at Windsor, Nova Scotia. The story as told in subsequent pages by Sheriff Bates is unique in criminal annals and is worthy of careful perusal. - Summary Adapted from the Preface

LibriVox volunteers bring you 17 recordings of On Christmas Eve by Katharine Lee Bates.<br> This was the Weekly Poetry project for December 19, 2021.<br> -------<br> Best known as the author of "America the Beautiful", American professor and poet Katharine Lee Bates also wrote many books and articles on social reform. In this poem, she strips away some of the outer layers of the Christmas story to peer into the core of the event. - Summary by TriciaG

LibriVox volunteers bring you 13 recordings of The Empty Room by Katharine Lee Bates. This was the Fortnightly Poetry project for December 19, 2021.<br> -------<br> Best known as the author of "America the Beautiful", American professor and poet Katharine Lee Bates also wrote many books and articles on social reform. - Summary by TriciaG

10Fish Story

By Clara Doty Bates

LibriVox volunteers bring you 12 recordings of A Fish Story by Clara Doty Bates.<br> This was the Fortnightly Poetry project for May 8, 2022. <br> ------<br> Clara Doty Bates was a 19th-century American author who published a number of volumes of poetry and juvenile literature. Many of these works were illustrated, the designs being furnished by her sister. This Fortnightly offers a silly fish story. - Summary by Wikipedia

LibriVox volunteers bring you 12 recordings of America the Beautiful by Katharine Lee Bates.<br> This was the Weekly Poetry project for July 3, 2022. <br> ------<br> In honor of The United States' 246th birthday on July 4th. Bates wrote the words as a poem originally entitled "Pikes Peak". It was first published in the Fourth of July 1895 edition of the church periodical, The Congregationalist. It was at that time that the poem was first entitled "America". - Summary by TriciaG & Wikipedia

12Seen and Unseen

By E. Katharine Bates

Novelist. Psychic investigator. Globe trotter. The multi-plane traveler, E. Katharine Bates, shares her phenomenal adventures on the cusp of the Twentieth Century in the autobiographical “Seen and Unseen”. Journey with this worthy companion! Enjoy the otherworldly experience! - Summary by Brian Fullen