Bug 184076 – [Win] Assertions.h: VC doesn't support GCC extension ##__VA_ARGS__

• Status: RESOLVED
• Resolution: FIXED
• Component: Web Template Framework

[Fujii Hironori]

[Win] Assertions.h: VC doesn't support GCC extension ##__VA_ARGS__

> ------ Build started: Project: WebKit (WebKit\WebKit), Configuration: Debug x64 ------
> ChildProcess.cpp
> c:\webkit\gb\source\webkit\shared\childprocess.cpp(63): error C2059: syntax error: ')'
> WebLoaderStrategy.cpp
> c:\webkit\gb\source\webkit\webprocess\network\webloaderstrategy.cpp(388): error C2059: syntax error: ')'
> WebPage.cpp
> c:\webkit\gb\source\webkit\webprocess\webpage\webpage.cpp(2226): error C2059: syntax error: ')'
> Done building project "WebKit.vcxproj" -- FAILED.
> ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========


[GCC] The C Preprocessor: Variadic Macros
https://gcc.gnu.org/onlinedocs/cpp/Variadic-Macros.html

[Fujii Hironori]

Created attachment 336649 [details]
Patch

[Keith Rollin]

How is it that this is not working in VC? We've been building under Windows for years without issue.

Why is only Assertions.h affected? ##__VA_ARGS__ is used in many other places in WebKit, too.

[Keith Rollin]

I've verified that the patch builds debug and release versions of Safari and that the expected logging is still emitted.

[Fujii Hironori]

Thank you for reviewing  and testing my patch.
There are two reasons.

The difference between ##__VA_ARGS__ and __VA_ARGS__ is ##__VA_ARGS__ removes a preceding comma if the number of variadic arguments is zero.
MSVC treats ##__VA_ARGS__ as same as __VA_ARGS__. Then, there is no problem if the number of variadic arguments is greater than zero.

I'm now trying to build WebKit2 for Windows port. Compilation errors of comment#0 are observed only in WebKit2.

[WebKit Commit Bot]

Comment on attachment 336649 [details]
Patch

Clearing flags on attachment: 336649

Committed r230058: <https://trac.webkit.org/changeset/230058>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/38976831>