[Mac] check-for-weak-vtables-and-externals should ignore symbols from system headers.

• Component: Platform
• Status: RESOLVED INVALID

[Hajime Morrita]

heck-for-weak-vtables-and-externals should ignore symbols from system headers
because the system header forces them to export and we cannot control it 
when we use WTF_EXPORT-based symbol visibility control.

For example, /usr/include/c++/4.2.1/new contains following line:
#pragma GCC visibility push(default)

Fortunately JSC depends on very few such C++ symbols so I think this relaxation doesn't harm.

[Hajime Morrita]

Created attachment 116038 [details]
Patch

[Mark Rowe (bdash)]

I don’t think silently allowing these symbols to be exported this is the right solution. Our frameworks should only be exporting symbols that they provide, not random symbols from system headers. Take a look at the definition of OTHER_LDFLAGS in WebKit2/Configurations/Base.xcconfig for the approach that we use to address this in the one framework we currently have that does not use an explicit symbol export list.

[Mark Rowe (bdash)]

Comment on attachment 116038 [details]
Patch

Marking as r- per above comment.

[Hajime Morrita]

(In reply to comment #2)
> I don’t think silently allowing these symbols to be exported this is the right solution. Our frameworks should only be exporting symbols that they provide, not random symbols from system headers. Take a look at the definition of OTHER_LDFLAGS in WebKit2/Configurations/Base.xcconfig for the approach that we use to address this in the one framework we currently have that does not use an explicit symbol export list.

Wow, this is exactly what I want. Thanks much for your advice!
Closing the bug since we don't need this change.