Bug 25437 – tcmalloc/Windows bug can cause random GetLastError() failures.

• Status: NEW
• Component: Platform

[Mike Belshe]

The latest release of tcmalloc for windows picks up an easy bug fix which can effect windows builds:

TlsGetValue() will call SetLastError(0).  If you have code which looks like:

   MakeSomeWindowsCall(foo());
   if (GetLastError()) { ... }

if foo() returns something which needs to be destructed, that can call into tcmalloc, which will use thread-local-storage, which will SetLastError(0).

Fix:  When calling TlsGetValue, do this:
    err = GetLastError()
    TlsGetValue()
    SetLastError(err)

[Ahmad Saleem]

If I search for 'TlsGetValue' in current code on GitHub, it is only in third party code like libwebrtc and ANGLE and not in WebKit / WebCore.

https://searchfox.org/wubkat/search?q=TlsGetValue&path=&case=false&regexp=false

@Fuji - just to get your input since it mentions 'Window'. Do we have any such impact or we can close this?