On Mon, 18 Oct 2021 at 12:48, Aaron Ballman <aa...@aaronballman.com> wrote:
> On Mon, Oct 18, 2021 at 3:33 PM Richard Smith <rich...@metafoo.co.uk> > wrote: > > > > On Sun, 17 Oct 2021 at 04:58, Aaron Ballman via cfe-commits < > cfe-commits@lists.llvm.org> wrote: > >> > >> > >> Author: Aaron Ballman > >> Date: 2021-10-17T07:54:48-04:00 > >> New Revision: 2edb89c746848c52964537268bf03e7906bf2542 > >> > >> URL: > https://github.com/llvm/llvm-project/commit/2edb89c746848c52964537268bf03e7906bf2542 > >> DIFF: > https://github.com/llvm/llvm-project/commit/2edb89c746848c52964537268bf03e7906bf2542.diff > >> > >> LOG: Lex arguments for __has_cpp_attribute and friends as expanded > tokens > >> > >> The C and C++ standards require the argument to __has_cpp_attribute and > >> __has_c_attribute to be expanded ([cpp.cond]p5). It would make little > sense > >> to expand the argument to those operators but not expand the argument to > >> __has_attribute and __has_declspec, so those were both also changed in > this > >> patch. > >> > >> Note that it might make sense for the other builtins to also expand > their > >> argument, but it wasn't as clear to me whether the behavior would be > correct > >> there, and so they were left for a future revision. > >> > >> Added: > >> clang/test/Preprocessor/has_attribute_errors.cpp > >> > >> Modified: > >> clang/docs/ReleaseNotes.rst > >> clang/lib/Lex/PPMacroExpansion.cpp > >> clang/test/Preprocessor/has_attribute.c > >> clang/test/Preprocessor/has_attribute.cpp > >> clang/test/Preprocessor/has_c_attribute.c > >> > >> Removed: > >> > >> > >> > >> > ################################################################################ > >> diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst > >> index 6501a4870e2a6..263eae83036df 100644 > >> --- a/clang/docs/ReleaseNotes.rst > >> +++ b/clang/docs/ReleaseNotes.rst > >> @@ -110,6 +110,13 @@ Attribute Changes in Clang > >> attribute is handled instead, e.g. in ``handleDeclAttribute``. > >> (This was changed in order to better support attributes in code > completion). > >> > >> +- __has_cpp_attribute, __has_c_attribute, __has_attribute, and > __has_declspec > >> + will now macro expand their argument. This causes a change in > behavior for > >> + code using ``__has_cpp_attribute(__clang__::attr)`` (and same for > >> + ``__has_c_attribute``) where it would previously expand to ``0`` for > all > >> + attributes, but will now issue an error due to the expansion of the > >> + predefined ``__clang__`` macro. > >> + > >> Windows Support > >> --------------- > >> > >> > >> diff --git a/clang/lib/Lex/PPMacroExpansion.cpp > b/clang/lib/Lex/PPMacroExpansion.cpp > >> index bf19f538647e6..5a0fa5184e38b 100644 > >> --- a/clang/lib/Lex/PPMacroExpansion.cpp > >> +++ b/clang/lib/Lex/PPMacroExpansion.cpp > >> @@ -1293,7 +1293,7 @@ static bool EvaluateHasIncludeNext(Token &Tok, > >> /// integer values. > >> static void EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& > OS, > >> Token &Tok, IdentifierInfo > *II, > >> - Preprocessor &PP, > >> + Preprocessor &PP, bool > ExpandArgs, > >> llvm::function_ref< > >> int(Token &Tok, > >> bool > &HasLexedNextTok)> Op) { > >> @@ -1319,7 +1319,10 @@ static void > EvaluateFeatureLikeBuiltinMacro(llvm::raw_svector_ostream& OS, > >> bool SuppressDiagnostic = false; > >> while (true) { > >> // Parse next token. > >> - PP.LexUnexpandedToken(Tok); > >> + if (ExpandArgs) > >> + PP.Lex(Tok); > >> + else > >> + PP.LexUnexpandedToken(Tok); > > > > > > How does this handle things like: > > > > #define RPAREN ) > > #if __has_attribute(clang::fallthrough RPAREN > > > > ? I think that should be an error: the ) token should not be produced by > macro expansion, analogous to the behavior of function-like macros. But I > imagine unless we're careful here, we'll allow that macro expansion to > terminate the "macro". > > I agree, I think that should be an error. We handle it reasonably too; I > get: > > error: missing ')' after 'clang' > > though it appears there is some compiler divergence here: > https://godbolt.org/z/c84cb3PW7 Oops, I meant __has_cpp_attribute, not __has_attribute. We mishandle that one just like GCC: https://godbolt.org/z/Ej84Kca16
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