Setting breakpoints using debug version(DWARF)

[Brian Gavin]

Hello,

I am excited to see the new ability to set breakpoints and view variables in Chrome.   

When I do a simple project with about 5 source files it works fairly well, but when I try to debug my large project with 100s of files.   I am unable to set breakpoints in the callback functions such as mouse events and our callback function that draws to the screen at 60 fps( emscripten_set_main_loop_arg ).   Is there a linker/compiler setting that helps this.   I am using -g -O0 -fno-inline as flags for debugging.   I am using emscripten SDK 2.0.11 with Chrome Canary.

Thanks,

Brian Gavin

[Philip Pfaffe]

Hi Brian!

By unable do you mean that all the line numbers in the sources panel are grayed out? But you can see all source files? Are you using those flags both for compiling and linking?

Cheers,

Philip

[Brian Gavin]

yes, all of the line numbers are grayed out, but I can see all of my source files.   I am using -g for linking and compiling -O0 only when linking.   I can set breakpoints in my main() function and any code in other files called by the main() function.

My code has a file main.cpp that holds int main()  if I hack my code and a callback function for an event or my main loop callback I can set breakpoints for code in main.cpp but as soon as my code calls code outside of main.cpp.   I can not set breakpoints in the code.

pseudo code

void MainLoopCB(void* data)

{

     // If this function is not in main.cpp breakpoints will not work

     ClassInOtherFile();

}

int main()

{

     // Breakpoints work here and variables can be inspected

     int i=0;

     int sum=0;

     for(i=0;i<20;i++)

     {

           sum++;

     }

       emscripten_set_main_loop_arg(MainLoopCB,0,nullptr,true);

      return 0;

[Philip Pfaffe]

Thanks for the infos! I tried to reproduce it with your pseudo code but had no luck. I can see breakable lines in the MainLoopCB file. Would you mind filing a bug at crbug.com against the Platform>DevTools>WebAssembly component?

If possible, please include a minimal self-contained reproducer, such as the two required sources and something like a makefile to build.  You might also attach a binary if that's not too big!

[chunyi song]

I also encountered the same problem when I debug a qt5 app with dwarf in chrome devtools. I can see all the c++ source files in devtool, but some source code line can not set breakpoints and some line can set bp in the same file, which are all grayed out.

[Brian Gavin]

Breakpoints are working much better with recent changes.   Still unable to see variable values in many cases and crashing, but nice improvements.  :)

[Philip Pfaffe]

Hi Brian,

great to hear that things improved!

I'd still like to get to the bottom of your remaining issues. What kind of crashes are you getting? Page/Renderer crashes or DevTools crashes? It would be great if you could share a reproducer, then I can debug what's going on!

Cheers,

Philip

[Brian Gavin]

DevTool crashes.   Unfortunately I do not have a simple example with repro steps.   

Sorry,

Brian Gavin

[Brian Gavin]

I also noticed adding -fno-inline to compiler options made things worse for setting breakpoints.

[Philip Pfaffe]

How does the DevTools crash look like? Do you get a "DevTools disconnected from the page" error or anything on the terminal? What Chrome version are you on currently?

It would be great if you could share steps to reproduce, as so far I've not managed to myself.

Cheers,
Philip

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[Brian Gavin]

I am running the latest version of chrome canary  91.0.4464.5  64bit MS Windows .   The crashing is pretty random.    You can set a breakpoint on a line and it might work and then you run some more and it crashes.   Yes I get a DevTools disconneted error and the web page crashes..

[Brian Gavin]

The crashing of DevTools when using Chrome Canary has gone away for me.   It used crash all the time which made it unusable.   Nice work to everyone creating this tool.  

The only issue I still see is inspecting local scope variables does not always work and will sometimes report undefined.

Brian Gavin