disable PDB of specific modules on linux

[Shanfeng Cheng]

Since debugging on linux is slow due to the large size of PDB, is there any option for us to exclude PDB for some of the modules? For example, we can exclude the PDB information of the webcore module if we are only debugging the browser-level code. 

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Stephen Cheng

[Nico Weber]

https://code.google.com/p/chromium/wiki/LinuxFasterBuilds#Build_WebKit_without_debug_symbols I haven't tried this, but looking at WebKit/Source/config.gyp it might still work.

Nico

ps: (PDB is a Visual Studio-specific file format that's not used on Linux.)

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[Shanfeng Cheng]

I did that and I wonder how to check if the debug information of webcore has been removed. The main executable file is still 600+ MB, same as before. I tried debugging it and the speed has no noticeable improvement. 

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Stephen Cheng

[Shanfeng Cheng]

In config.gyp, there is a comment saying that it is for gcc only. I guess it is not valid for clang which we are currently using?

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Shanfeng Cheng

 

From: Nico Weber

Date: 2014-12-01 11:20

To: Shanfeng Cheng

CC: chromium-dev

Subject: Re: [chromium-dev] disable PDB of specific modules on linux

[Nico Weber]

That comment looks incorrect.

You can build with ninja -v and check that `-g` isn't passed to the compiler for blink object files. Or you can look at the generated ninja files for blink (e.g. out/Release/obj/third_party/WebKit/Source/core/webcore_html.ninja) and check that -g isn't passed in cflags.

[Shanfeng Cheng]

The -g flag has been successfully removed. But I compared the folder out/Debug/obj/third_party/WebKit/Source/core between two builds with different settings. The lib*.a files under that folder have similar file sizes.  

[Nico Weber]

Do the generated cflags when you don't disable symbols include -gsplit-dwarf? If so, the debug info is written into a separate .dwo file, not into the .o files – hence, the size of the .o files is expected to be roughly identical with and without debug info in both cases.

[Shanfeng Cheng]

Yes. It has -gsplit-dwarf. However, both builds have many smaller dwo files and they are about the same size. 

[Nico Weber]

If you're doing both builds in the same build directory, the build with debug info will write .dwo files and the build without debug info won't use those but it won't delete them either. If you remove the .dwo files for blink and rebuild without debug info, do they come back?

[Shanfeng Cheng]

I found the problem. I had to remove the option -gsplit-dwarf as well in order to completely get rid of the .dwo files. If only -g is removed while -gsplit-dwarf stays, it still generates the debugging information.