If a module A exports a macro M, and a module B imports that macro and #undef's

it, importers of B should not see the macro. This is complicated by the fact
that A's macro could also be visible through a different path. The rules (as
hashed out on cfe-commits) are included as a documentation update in this
change.

With this, the number of regressions in libc++'s testsuite when modules are
enabled drops from 47 to 7. Those remaining 7 are also macro-related, and are
due to remaining bugs in this change (in particular, the handling of submodules
is imperfect).

llvm-svn: 202560

1 files changed, 5 insertions, 5 deletions

diff --git a/clang/lib/Lex/PPMacroExpansion.cpp b/clang/lib/Lex/PPMacroExpansion.cpp
index 721760afa0e..84f1ea5b1fa 100644
--- a/clang/lib/Lex/PPMacroExpansion.cpp
+++ b/clang/lib/Lex/PPMacroExpansion.cpp
@@ -293,11 +293,11 @@ bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
     for (MacroDirective::DefInfo PrevDef = Def.getPreviousDefinition();
          PrevDef && !PrevDef.isUndefined();
          PrevDef = PrevDef.getPreviousDefinition()) {
-      if (PrevDef.getDirective()->isAmbiguous()) {
-        Diag(PrevDef.getMacroInfo()->getDefinitionLoc(),
-             diag::note_pp_ambiguous_macro_other)
-          << Identifier.getIdentifierInfo();
-      }
+      Diag(PrevDef.getMacroInfo()->getDefinitionLoc(),
+           diag::note_pp_ambiguous_macro_other)
+        << Identifier.getIdentifierInfo();
+      if (!PrevDef.getDirective()->isAmbiguous())
+        break;
     }
   }