================
@@ -1880,16 +1880,70 @@ Sema::ConditionResult
Parser::ParseCXXCondition(StmtResult *InitStmt,
return Sema::ConditionError();
}
+ if (!getLangOpts().CPlusPlus && Tok.is(tok::kw___extension__)) {
+ // In C, the first clause of a condition may be a declaration used as an
+ // init-statement (C2y), and that declaration may be prefixed by one or
more
+ // __extension__ markers. Consume them up front -- mirroring
block-statement
+ // parsing -- so the disambiguation below sees the real start of the
+ // declaration. The markers also silence extension diagnostics for the rest
+ // of the condition, including the diagnostic for the init-statement
+ // extension itself.
+ std::optional<ExtensionRAIIObject> ExtensionGuard;
+ ExtensionGuard.emplace(Diags);
+ while (TryConsumeToken(tok::kw___extension__))
+ ;
+ }
+
ParsedAttributes attrs(AttrFactory);
- MaybeParseCXX11Attributes(attrs);
+ bool ParsedAttrs = MaybeParseCXX11Attributes(attrs);
+ if (!getLangOpts().CPlusPlus)
----------------
AaronBallman wrote:
I think there's a GCC bug in the C implementation for `[[]]` because `[[]];` is
a declaration (an attribute-declaration, specifically). And that makes me
wonder if rejecting `__attribute__` in that same position is also a bug:
https://godbolt.org/z/G1Ks5f5Yr
Another oddity that makes me think this could be a bug is that it is accepted
in C++ mode, while `[[]];` is not: https://godbolt.org/z/nrx8nYxxd
But then again, GCC is consistent about expecting an actual declaration as
opposed to "it was easier for the standards committee to specify the grammar if
this is a declaration" things: https://godbolt.org/z/E1a1xjrc1 so perhaps this
is intentional?
CC @pinskia
https://github.com/llvm/llvm-project/pull/198244
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