[modules] Re-enable the "ambiguous expansion of macro" warning.

Also update "test/Modules/macros.c" to test modified semantics:
-When there is an ambiguous macro, expand using the latest introduced version, not the first one.
-#undefs in submodules cause the macro to not be exported by that submodule, it doesn't cause
 undefining of macros in the translation unit that imported that submodule.
 This reduces macro namespace interference across modules.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178105 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 24 insertions, 25 deletions

diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index bb2634ffb6..21451f581f 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -211,7 +211,9 @@ bool Preprocessor::isNextPPTokenLParen() {
 /// expanded as a macro, handle it and return the next token as 'Identifier'.
 bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
                                                  MacroDirective *MD) {
-  MacroInfo *MI = MD->getMacroInfo();
+  MacroDirective::DefInfo Def = MD->getDefinition();
+  assert(Def.isValid());
+  MacroInfo *MI = Def.getMacroInfo();
 
   // If this is a macro expansion in the "#if !defined(x)" line for the file,
   // then the macro could expand to different things in other contexts, we need
@@ -286,25 +288,22 @@ bool Preprocessor::HandleMacroExpandedIdentifier(Token &Identifier,
     }
   }
 
-  // FIXME: Temporarily disable this warning that is currently bogus with a PCH
-  // that redefined a macro without undef'ing it first (test/PCH/macro-redef.c).
-#if 0
   // If the macro definition is ambiguous, complain.
-  if (MI->isAmbiguous()) {
+  if (Def.getDirective()->isAmbiguous()) {
     Diag(Identifier, diag::warn_pp_ambiguous_macro)
       << Identifier.getIdentifierInfo();
     Diag(MI->getDefinitionLoc(), diag::note_pp_ambiguous_macro_chosen)
       << Identifier.getIdentifierInfo();
-    for (MacroInfo *PrevMI = MI->getPreviousDefinition();
-         PrevMI && PrevMI->isDefined();
-         PrevMI = PrevMI->getPreviousDefinition()) {
-      if (PrevMI->isAmbiguous()) {
-        Diag(PrevMI->getDefinitionLoc(), diag::note_pp_ambiguous_macro_other)
+    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();
       }
     }
   }
-#endif
 
   // If we started lexing a macro, enter the macro expansion body.
 
diff --git a/test/Modules/macros.c b/test/Modules/macros.c
index 406e554a7a..c715ec9651 100644
--- a/test/Modules/macros.c
+++ b/test/Modules/macros.c
@@ -1,4 +1,3 @@
-// XFAIL: *
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -fmodules -x objective-c -emit-module -fmodules-cache-path=%t -fmodule-name=macros_top %S/Inputs/module.map
 // RUN: %clang_cc1 -fmodules -x objective-c -emit-module -fmodules-cache-path=%t -fmodule-name=macros_left %S/Inputs/module.map
@@ -10,12 +9,12 @@
 // These notes come from headers in modules, and are bogus.
 
 // FIXME: expected-note{{previous definition is here}}
+// FIXME: expected-note{{previous definition is here}} expected-note{{expanding this definition of 'LEFT_RIGHT_DIFFERENT'}}
+// expected-note{{other definition of 'TOP_RIGHT_REDEF'}} expected-note{{expanding this definition of 'LEFT_RIGHT_DIFFERENT2'}}
 // expected-note{{other definition of 'LEFT_RIGHT_DIFFERENT'}}
-// expected-note{{expanding this definition of 'TOP_RIGHT_REDEF'}}
-// FIXME: expected-note{{previous definition is here}} \
-// expected-note{{expanding this definition of 'LEFT_RIGHT_DIFFERENT'}}
 
-// expected-note{{other definition of 'TOP_RIGHT_REDEF'}}
+
+// expected-note{{expanding this definition of 'TOP_RIGHT_REDEF'}}
 
 @import macros;
 
@@ -80,8 +79,8 @@ void f() {
 #  error TOP should be visible
 #endif
 
-#ifdef TOP_LEFT_UNDEF
-#  error TOP_LEFT_UNDEF should not be visible
+#ifndef TOP_LEFT_UNDEF
+#  error TOP_LEFT_UNDEF should still be defined
 #endif
 
 void test1() {
@@ -89,7 +88,8 @@ void test1() {
   TOP_RIGHT_REDEF *ip = &i;
 }
 
-#define LEFT_RIGHT_DIFFERENT2 double // FIXME: expected-warning{{'LEFT_RIGHT_DIFFERENT2' macro redefined}}
+#define LEFT_RIGHT_DIFFERENT2 double // FIXME: expected-warning{{'LEFT_RIGHT_DIFFERENT2' macro redefined}} \
+                                     // expected-note{{other definition of 'LEFT_RIGHT_DIFFERENT2'}}
 
 // Import right module (which also imports top)
 @import macros_right;
@@ -112,11 +112,11 @@ void test2() {
   int i;
   float f;
   double d;
-  TOP_RIGHT_REDEF *ip = &i; // expected-warning{{ambiguous expansion of macro 'TOP_RIGHT_REDEF'}}
+  TOP_RIGHT_REDEF *fp = &f; // expected-warning{{ambiguous expansion of macro 'TOP_RIGHT_REDEF'}}
   
-  LEFT_RIGHT_IDENTICAL *ip2 = &i;
-  LEFT_RIGHT_DIFFERENT *fp = &f; // expected-warning{{ambiguous expansion of macro 'LEFT_RIGHT_DIFFERENT'}}
-  LEFT_RIGHT_DIFFERENT2 *dp = &d;
+  LEFT_RIGHT_IDENTICAL *ip = &i;
+  LEFT_RIGHT_DIFFERENT *ip2 = &i; // expected-warning{{ambiguous expansion of macro 'LEFT_RIGHT_DIFFERENT'}}
+  LEFT_RIGHT_DIFFERENT2 *ip3 = &i; // expected-warning{{ambiguous expansion of macro 'LEFT_RIGHT_DIFFERENT2}}
   int LEFT_RIGHT_DIFFERENT3;
 }
 
@@ -133,6 +133,6 @@ void test3() {
 
 @import macros_right.undef;
 
-#ifdef TOP_RIGHT_UNDEF
-# error TOP_RIGHT_UNDEF should not be defined
+#ifndef TOP_RIGHT_UNDEF
+# error TOP_RIGHT_UNDEF should still be defined
 #endif