aaron.ballman added inline comments.
================ Comment at: clang/lib/Sema/Sema.cpp:2421-2428 + // Perform a lookup at TUScope. If it succeeds, we're at global scope and a + // single '_' is enough to be reserved. + LookupResult IdentifierLookup(*this, II, SourceLocation(), + Sema::LookupAnyName, + Sema::ForExternalRedeclaration); + IdentifierLookup.suppressDiagnostics(); + if (LookupName(IdentifierLookup, TUScope)) ---------------- rsmith wrote: > I don't understand why name lookup is involved here. Whether an identifier is > reserved doesn't depend on whether it's already been declared in the global > namespace or not. It's valid to declare `_foo` in some user-defined namespace > regardless of whether there's already a `_foo` in the global namespace, and > it's invalid to declare `_foo` in the global namespace regardless of whether > there's already a `_foo` in the global namespace. > > If you're trying to detect whether the name is being introduced in the global > namespace scope, per C++ [lex.name]/3.2, you can't do that like this; you'll > need to look at the `DeclContext` of the declaration instead of just the > identifier. Sorry @serge-sans-paille for my think-o, Richard is right. My thinking was "if the declaration can be found at the global namespace, then it's reserved", but.. that's a hypothetical declaration, not an actual one, so of course the name lookup won't find it. Derp. I guess we really do have to look at the `DeclContext`. @rsmith -- just to be clear, from http://eel.is/c++draft/lex.name#3.2, does "for use as a name in the global namespace" imply macros as well? e.g., can an implementation decide to use this reservation to `#define _foo 12`, which would cause problems with a `_foo` declared in a user-defined namespace? If so, then we can ignore what the declaration context is because the name could be snatched out from under the user via a macro anyway. CHANGES SINCE LAST ACTION https://reviews.llvm.org/D93095/new/ https://reviews.llvm.org/D93095 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
