Compiler error when using "_Generic" identifier in C++ source code

[llvmbot]

Bugzilla Link	11261
Resolution	WONTFIX
Resolved on	Oct 28, 2011 18:01
Version	trunk
OS	MacOS X
Reporter	LLVM Bugzilla Contributor
CC	@DougGregor

Extended Description

When compiling code with clang++ 3.0 (as shipped with Apple XCode 4.2) that contains _Generic, an error is raised, like this:

test.cc:5:6: error: expected unqualified-id
int _Generic = 0;

After some googling around, this seems to be related to the "C1X generic selections" extension (see http://clang.llvm.org/doxygen/classclang_1_1GenericSelectionExpr.html). However, I could not find further information on this, and it is not clear to me whether this is part of C++11, or of a future extension of the C++ standard.

If this error really is intentional behavior, then please change the warning to something more helpful, like "_Generic is a C1X reserved keyword".

But personally I'd prefer if using _Generic was again made possible for code that does not explicitly request C1X extensions, as "legacy code" is using this.

For reference, this was with
Apple clang version 3.0 (tags/Apple/clang-211.10.1) (based on LLVM 3.0svn)
Target: x86_64-apple-darwin10.8.0
Thread model: posix

[lattner]

Note that identifiers that start with an underscore and capital letter are in the implementation reserved namespace. You're not supposed to use them in your code.

[DougGregor]

Since _Generic is (and has always been) a reserved name, so user code that's using this name has always been non-conforming. For that reason, and because likely that people want to use _Generic in (say) C++ or C99 mode, I'm closing this as "won't fix".