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

5 files changed, 101 insertions, 53 deletions

diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 0b36d58806a..77a47b8861d 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -1588,6 +1588,9 @@ public:
   void CheckShadow(Scope *S, VarDecl *D, const LookupResult& R);
   void CheckShadow(Scope *S, VarDecl *D);
   void CheckCastAlign(Expr *Op, QualType T, SourceRange TRange);
+  void handleTagNumbering(const TagDecl *Tag, Scope *TagScope);
+  void setTagNameForLinkagePurposes(TagDecl *TagFromDeclSpec,
+                                    TypedefNameDecl *NewTD);
   void CheckTypedefForVariablyModifiedType(Scope *S, TypedefNameDecl *D);
   NamedDecl* ActOnTypedefDeclarator(Scope* S, Declarator& D, DeclContext* DC,
                                     TypeSourceInfo *TInfo,
@@ -3989,7 +3992,8 @@ public:
                               SourceLocation UsingLoc,
                               UnqualifiedId &Name,
                               AttributeList *AttrList,
-                              TypeResult Type);
+                              TypeResult Type,
+                              Decl *DeclFromDeclSpec);
 
   /// BuildCXXConstructExpr - Creates a complete call to a constructor,
   /// including handling of its default argument expressions.
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 04bb4405cbf..4e58ca345fb 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -558,6 +558,7 @@ Decl *Parser::ParseUsingDeclaration(unsigned Context,
   // Maybe this is an alias-declaration.
   TypeResult TypeAlias;
   bool IsAliasDecl = Tok.is(tok::equal);
+  Decl *DeclFromDeclSpec = nullptr;
   if (IsAliasDecl) {
     // If we had any misplaced attributes from earlier, this is where they
     // should have been written.
@@ -612,10 +613,12 @@ Decl *Parser::ParseUsingDeclaration(unsigned Context,
       Diag(SS.getBeginLoc(), diag::err_alias_declaration_not_identifier)
         << FixItHint::CreateRemoval(SS.getRange());
 
-    TypeAlias = ParseTypeName(nullptr, TemplateInfo.Kind ?
-                              Declarator::AliasTemplateContext :
-                              Declarator::AliasDeclContext, AS, OwnedType,
-                              &Attrs);
+    TypeAlias = ParseTypeName(nullptr, TemplateInfo.Kind
+                                           ? Declarator::AliasTemplateContext
+                                           : Declarator::AliasDeclContext,
+                              AS, &DeclFromDeclSpec, &Attrs);
+    if (OwnedType)
+      *OwnedType = DeclFromDeclSpec;
   } else {
     // C++11 attributes are not allowed on a using-declaration, but GNU ones
     // are.
@@ -664,7 +667,7 @@ Decl *Parser::ParseUsingDeclaration(unsigned Context,
       TemplateParams ? TemplateParams->size() : 0);
     return Actions.ActOnAliasDeclaration(getCurScope(), AS, TemplateParamsArg,
                                          UsingLoc, Name, Attrs.getList(),
-                                         TypeAlias);
+                                         TypeAlias, DeclFromDeclSpec);
   }
 
   return Actions.ActOnUsingDeclaration(getCurScope(), AS,
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;
   }
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 57d9ad264e7..45ba685d118 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -8474,7 +8474,8 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S,
                                   SourceLocation UsingLoc,
                                   UnqualifiedId &Name,
                                   AttributeList *AttrList,
-                                  TypeResult Type) {
+                                  TypeResult Type,
+                                  Decl *DeclFromDeclSpec) {
   // Skip up to the relevant declaration scope.
   while (S->getFlags() & Scope::TemplateParamScope)
     S = S->getParent();
@@ -8602,6 +8603,10 @@ Decl *Sema::ActOnAliasDeclaration(Scope *S,
 
     NewND = NewDecl;
   } else {
+    if (auto *TD = dyn_cast_or_null<TagDecl>(DeclFromDeclSpec)) {
+      setTagNameForLinkagePurposes(TD, NewTD);
+      handleTagNumbering(TD, S);
+    }
     ActOnTypedefNameDecl(S, CurContext, NewTD, Previous, Redeclaration);
     NewND = NewTD;
   }
diff --git a/clang/test/CodeGenCXX/mangle.cpp b/clang/test/CodeGenCXX/mangle.cpp
index 34f091d0369..5012c3b3798 100644
--- a/clang/test/CodeGenCXX/mangle.cpp
+++ b/clang/test/CodeGenCXX/mangle.cpp
@@ -1071,3 +1071,33 @@ auto f4(T... x) -> decltype(operator+(x...));
 // CHECK-LABEL: @_ZN6test522f4IJNS_1XEEEEDTclonplspfp_EEDpT_
 void use() { f4(X{}); }
 }
+
+namespace test53 {
+struct c {
+  using t1 = struct { int z; };
+  using t2 = struct { double z; };
+  using t3 = struct { float z; };
+  using t4 = struct { float z; };
+
+  __attribute__((used)) c(t1) {}
+  __attribute__((used)) c(t2) {}
+  __attribute__((used)) c(t3) {}
+  __attribute__((used)) c(t4) {}
+  // CHECK-LABEL: @_ZN6test531cC2ENS0_2t1E
+  // CHECK-LABEL: @_ZN6test531cC2ENS0_2t2E
+  // CHECK-LABEL: @_ZN6test531cC2ENS0_2t3E
+  // CHECK-LABEL: @_ZN6test531cC2ENS0_2t4E
+};
+}
+
+namespace test54 {
+struct c {
+  using t1 = struct { int z; } *;
+  using t2 = struct { double z; } *;
+
+  __attribute__((used)) c(t1) {}
+  __attribute__((used)) c(t2) {}
+  // CHECK-LABEL: @_ZN6test541cC2EPNS0_Ut_E
+  // CHECK-LABEL: @_ZN6test541cC2EPNS0_Ut0_E
+};
+}