[Modules] Fix an identifier hiding a function-like macro definition. (#135471)

We emit a macro definition only in a module defining it. But it means
that if another module has an identifier with the same name as the
macro, the users of such module won't be able to use the macro anymore.

Fix by storing that an identifier has a macro definition that's not in a
current module (`MacroDirectivesOffset == 0`). This way
`IdentifierLookupVisitor` knows not to stop at the first module with an
identifier but to keep checking included modules for the actual macro
definition.

Fixes issue #32040.

rdar://30258278

1 files changed, 11 insertions, 5 deletions

diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 95b5718..8c261e1 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -3795,7 +3795,10 @@ bool IsInterestingIdentifier(const IdentifierInfo *II, uint64_t MacroOffset,
       II->getNotableIdentifierID() != tok::NotableIdentifierKind::not_notable ||
       II->getBuiltinID() != Builtin::ID::NotBuiltin ||
       II->getObjCKeywordID() != tok::ObjCKeywordKind::objc_not_keyword;
-  if (MacroOffset || II->isPoisoned() || (!IsModule && IsInteresting) ||
+  if (MacroOffset ||
+      (II->hasMacroDefinition() &&
+       II->hasFETokenInfoChangedSinceDeserialization()) ||
+      II->isPoisoned() || (!IsModule && IsInteresting) ||
       II->hasRevertedTokenIDToIdentifier() ||
       (NeedDecls && II->getFETokenInfo()))
     return true;
@@ -3874,7 +3877,8 @@ public:
     if (isInterestingIdentifier(II, MacroOffset)) {
       DataLen += 2; // 2 bytes for builtin ID
       DataLen += 2; // 2 bytes for flags
-      if (MacroOffset)
+      if (MacroOffset || (II->hasMacroDefinition() &&
+                          II->hasFETokenInfoChangedSinceDeserialization()))
         DataLen += 4; // MacroDirectives offset.
 
       if (NeedDecls && IdResolver)
@@ -3905,15 +3909,17 @@ public:
     assert((Bits & 0xffff) == Bits && "ObjCOrBuiltinID too big for ASTReader.");
     LE.write<uint16_t>(Bits);
     Bits = 0;
-    bool HadMacroDefinition = MacroOffset != 0;
-    Bits = (Bits << 1) | unsigned(HadMacroDefinition);
+    bool HasMacroDefinition =
+        (MacroOffset != 0) || (II->hasMacroDefinition() &&
+                               II->hasFETokenInfoChangedSinceDeserialization());
+    Bits = (Bits << 1) | unsigned(HasMacroDefinition);
     Bits = (Bits << 1) | unsigned(II->isExtensionToken());
     Bits = (Bits << 1) | unsigned(II->isPoisoned());
     Bits = (Bits << 1) | unsigned(II->hasRevertedTokenIDToIdentifier());
     Bits = (Bits << 1) | unsigned(II->isCPlusPlusOperatorKeyword());
     LE.write<uint16_t>(Bits);
 
-    if (HadMacroDefinition)
+    if (HasMacroDefinition)
       LE.write<uint32_t>(MacroOffset);
 
     if (NeedDecls && IdResolver) {