This matches a similar behavior with GCC accepting [[gnu::__attr__]] as a alias for [[gnu::attr]] in that clang attributes can now be spelled with two leading and trailing underscores.
I had always intended for this to work, but missed the critical bit. We already had an existing test in test/Preprocessor/has_attribute.cpp for [[clang::__fallthrough__]] but using that spelling would still give an "unknown attribute" diagnostic.
llvm-svn: 346547
Currently, we only accept clang as the scoped attribute identifier for double square bracket attributes provided by Clang, but this has the potential to conflict with user-defined macros. To help alleviate these concerns, this introduces the _Clang scoped attribute identifier as an alias for clang. It also introduces a warning with a fixit on the off chance someone attempts to use __clang__ as the scoped attribute (which is a predefined compiler identification macro).
llvm-svn: 346521
conflicting attribute, warn about the conflict and pick a "winning"
attribute to preserve, instead of emitting an error. This matches the
behavior when the conflicting attributes are on different declarations.
Along the way I discovered that conflicts involving __forceinline were
reported as 'always_inline' (alternate spelling, same attribute) so
fixed that up to report the attribute as spelled in the source.
llvm-svn: 225813
Aaron Ballman