Sema: Properly track mangling number/name for linkage for using decls

Using declarations which are aliases to struct types have their name
used as the struct type's name for linkage purposes.  Otherwise, make
sure to give an anonymous struct defined inside a using declaration a
mangling number to disambiguate it from other anonymous structs in the
same context.

This fixes PR22809.

llvm-svn: 231909

1 files changed, 52 insertions, 46 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index e9b0f5a3fbd..dc428569bea 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -3416,8 +3416,8 @@ Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
   return ParsedFreeStandingDeclSpec(S, AS, DS, MultiTemplateParamsArg());
 }
 
-static void HandleTagNumbering(Sema &S, const TagDecl *Tag, Scope *TagScope) {
-  if (!S.Context.getLangOpts().CPlusPlus)
+void Sema::handleTagNumbering(const TagDecl *Tag, Scope *TagScope) {
+  if (!Context.getLangOpts().CPlusPlus)
     return;
 
   if (isa<CXXRecordDecl>(Tag->getParent())) {
@@ -3426,23 +3426,63 @@ static void HandleTagNumbering(Sema &S, const TagDecl *Tag, Scope *TagScope) {
     if (!Tag->getName().empty() || Tag->getTypedefNameForAnonDecl())
       return;
     MangleNumberingContext &MCtx =
-        S.Context.getManglingNumberContext(Tag->getParent());
-    S.Context.setManglingNumber(
+        Context.getManglingNumberContext(Tag->getParent());
+    Context.setManglingNumber(
         Tag, MCtx.getManglingNumber(Tag, TagScope->getMSLocalManglingNumber()));
     return;
   }
 
   // If this tag isn't a direct child of a class, number it if it is local.
   Decl *ManglingContextDecl;
-  if (MangleNumberingContext *MCtx =
-          S.getCurrentMangleNumberContext(Tag->getDeclContext(),
-                                          ManglingContextDecl)) {
-    S.Context.setManglingNumber(
+  if (MangleNumberingContext *MCtx = getCurrentMangleNumberContext(
+          Tag->getDeclContext(), ManglingContextDecl)) {
+    Context.setManglingNumber(
         Tag,
         MCtx->getManglingNumber(Tag, TagScope->getMSLocalManglingNumber()));
   }
 }
 
+void Sema::setTagNameForLinkagePurposes(TagDecl *TagFromDeclSpec,
+                                        TypedefNameDecl *NewTD) {
+  // Do nothing if the tag is not anonymous or already has an
+  // associated typedef (from an earlier typedef in this decl group).
+  if (TagFromDeclSpec->getIdentifier())
+    return;
+  if (TagFromDeclSpec->getTypedefNameForAnonDecl())
+    return;
+
+  // A well-formed anonymous tag must always be a TUK_Definition.
+  assert(TagFromDeclSpec->isThisDeclarationADefinition());
+
+  // The type must match the tag exactly;  no qualifiers allowed.
+  if (!Context.hasSameType(NewTD->getUnderlyingType(),
+                           Context.getTagDeclType(TagFromDeclSpec)))
+    return;
+
+  // If we've already computed linkage for the anonymous tag, then
+  // adding a typedef name for the anonymous decl can change that
+  // linkage, which might be a serious problem.  Diagnose this as
+  // unsupported and ignore the typedef name.  TODO: we should
+  // pursue this as a language defect and establish a formal rule
+  // for how to handle it.
+  if (TagFromDeclSpec->hasLinkageBeenComputed()) {
+    Diag(NewTD->getLocation(), diag::err_typedef_changes_linkage);
+
+    SourceLocation tagLoc = TagFromDeclSpec->getInnerLocStart();
+    tagLoc = getLocForEndOfToken(tagLoc);
+
+    llvm::SmallString<40> textToInsert;
+    textToInsert += ' ';
+    textToInsert += NewTD->getIdentifier()->getName();
+    Diag(tagLoc, diag::note_typedef_changes_linkage)
+        << FixItHint::CreateInsertion(tagLoc, textToInsert);
+    return;
+  }
+
+  // Otherwise, set this is the anon-decl typedef for the tag.
+  TagFromDeclSpec->setTypedefNameForAnonDecl(NewTD);
+}
+
 /// ParsedFreeStandingDeclSpec - This method is invoked when a declspec with
 /// no declarator (e.g. "struct foo;") is parsed. It also accepts template
 /// parameters to cope with template friend declarations.
@@ -3472,7 +3512,7 @@ Decl *Sema::ParsedFreeStandingDeclSpec(Scope *S, AccessSpecifier AS,
   }
 
   if (Tag) {
-    HandleTagNumbering(*this, Tag, S);
+    handleTagNumbering(Tag, S);
     Tag->setFreeStanding();
     if (Tag->isInvalidDecl())
       return Tag;
@@ -9720,7 +9760,7 @@ Sema::DeclGroupPtrTy Sema::FinalizeDeclaratorGroup(Scope *S, const DeclSpec &DS,
 
   if (DeclSpec::isDeclRep(DS.getTypeSpecType())) {
     if (TagDecl *Tag = dyn_cast_or_null<TagDecl>(DS.getRepAsDecl())) {
-      HandleTagNumbering(*this, Tag, S);
+      handleTagNumbering(Tag, S);
       if (!Tag->hasNameForLinkage() && !Tag->hasDeclaratorForAnonDecl())
         Tag->setDeclaratorForAnonDecl(FirstDeclaratorInGroup);
     }
@@ -10935,44 +10975,10 @@ TypedefDecl *Sema::ParseTypedefDecl(Scope *S, Declarator &D, QualType T,
   case TST_union:
   case TST_class: {
     TagDecl *tagFromDeclSpec = cast<TagDecl>(D.getDeclSpec().getRepAsDecl());
-
-    // Do nothing if the tag is not anonymous or already has an
-    // associated typedef (from an earlier typedef in this decl group).
-    if (tagFromDeclSpec->getIdentifier()) break;
-    if (tagFromDeclSpec->getTypedefNameForAnonDecl()) break;
-
-    // A well-formed anonymous tag must always be a TUK_Definition.
-    assert(tagFromDeclSpec->isThisDeclarationADefinition());
-
-    // The type must match the tag exactly;  no qualifiers allowed.
-    if (!Context.hasSameType(T, Context.getTagDeclType(tagFromDeclSpec)))
-      break;
-
-    // If we've already computed linkage for the anonymous tag, then
-    // adding a typedef name for the anonymous decl can change that
-    // linkage, which might be a serious problem.  Diagnose this as
-    // unsupported and ignore the typedef name.  TODO: we should
-    // pursue this as a language defect and establish a formal rule
-    // for how to handle it.
-    if (tagFromDeclSpec->hasLinkageBeenComputed()) {
-      Diag(D.getIdentifierLoc(), diag::err_typedef_changes_linkage);
-
-      SourceLocation tagLoc = D.getDeclSpec().getTypeSpecTypeLoc();
-      tagLoc = getLocForEndOfToken(tagLoc);
-
-      llvm::SmallString<40> textToInsert;
-      textToInsert += ' ';
-      textToInsert += D.getIdentifier()->getName();
-      Diag(tagLoc, diag::note_typedef_changes_linkage)
-        << FixItHint::CreateInsertion(tagLoc, textToInsert);
-      break;
-    }
-
-    // Otherwise, set this is the anon-decl typedef for the tag.
-    tagFromDeclSpec->setTypedefNameForAnonDecl(NewTD);
+    setTagNameForLinkagePurposes(tagFromDeclSpec, NewTD);
     break;
   }
-    
+
   default:
     break;
   }