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Do not apply calling conventions to MSVC entry points
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Authored by eandrews on Tue, Sep 15, 8:24 AM.

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Summary

Fix link error for MSVC entry points when calling conventions are specified. MSVC entry points should have default calling convention.

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Event Timeline

eandrews requested review of this revision.Tue, Sep 15, 8:24 AM
eandrews created this revision.
rnk accepted this revision.Tue, Sep 15, 11:23 AM

lgtm, thanks.

This revision is now accepted and ready to land.Tue, Sep 15, 11:23 AM
This revision was automatically updated to reflect the committed changes.
Herald added a project: Restricted Project. · View Herald TranscriptWed, Sep 16, 9:42 AM
In D87701#2274860, @rnk wrote:

lgtm, thanks.

Thanks for taking a look!

This is causing a link error in the windows chromium build:

lld-link: error: undefined symbol: _WinMain@16

referenced by D:\agent\_work\4\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:102

msvcrtd.lib(exe_winmain.obj):(int __cdecl invoke_main(void))

whoops, sorry for weird formatting in the previous comment.

I'll revert for now.

dmajor added a subscriber: dmajor.Thu, Sep 17, 1:41 PM

This broke Firefox builds too, in one of our helper binaries that uses a wWinMain, although I'm having trouble writing a minimal reproducer for it. Simply making a barebones wWinMain program doesn't hit the error.

If the patch re-lands, please cc me and I'll re-test.

This broke Firefox builds too, in one of our helper binaries that uses a wWinMain, although I'm having trouble writing a minimal reproducer for it. Simply making a barebones wWinMain program doesn't hit the error.

If the patch re-lands, please cc me and I'll re-test.

Will do. I think MSVC applies calling conventions to entry points when it is specified in function signature.

int WinMain(int argc) {return 1;}

Compiling this with /Gr generates symbol _WinMain@4 , meaning /Gr was ignored and fastcall was not applied to WinMain. But,

int __fastcall WinMain(int argc) {return 1;}

generates symbol @WinMain@4, meaning __fastcall calling convention was applied to WinMain.

It also looks like stdcall is default calling convention for WinMain.

Anyway, I'll upload a new patch for review once I understand the required behavior better.