[Modules] Implement ODR-like semantics for tag types in C/ObjC

Allow ODR for ObjC/C in the sense that we won't keep more that
one definition around (merge them). However, ensure the decl
pass the structural compatibility check in C11 6.2.7/1, for that,
reuse the structural equivalence checks used by the ASTImporter.

Few other considerations:
- Create error diagnostics for tag types mismatches and thread
them into the structural equivalence checks.
- Note that by doing this we only support redefinition between types
that are considered "compatible types" by C.

This is mixed approach of the suggestions discussed in
http://lists.llvm.org/pipermail/cfe-dev/2017-March/053257.html

Differential Revision: https://reviews.llvm.org/D31778

rdar://problem/31909368

llvm-svn: 306918

clang/include/clang/AST/ASTStructuralEquivalence.h

@@ -62,9 +62,11 @@ struct StructuralEquivalenceContext {
   StructuralEquivalenceContext(
       ASTContext &FromCtx, ASTContext &ToCtx,
       llvm::DenseSet<std::pair<Decl *, Decl *>> &NonEquivalentDecls,
-      bool StrictTypeSpelling = false, bool Complain = true)
+      bool StrictTypeSpelling = false, bool Complain = true,
+      bool ErrorOnTagTypeMismatch = false)
       : FromCtx(FromCtx), ToCtx(ToCtx), NonEquivalentDecls(NonEquivalentDecls),
-        StrictTypeSpelling(StrictTypeSpelling), Complain(Complain),
+        StrictTypeSpelling(StrictTypeSpelling),
+        ErrorOnTagTypeMismatch(ErrorOnTagTypeMismatch), Complain(Complain),
         LastDiagFromC2(false) {}
 
   DiagnosticBuilder Diag1(SourceLocation Loc, unsigned DiagID);

clang/include/clang/Basic/DiagnosticASTKinds.td

@@ -200,12 +200,17 @@ def note_odr_defined_here : Note<"also defined here">;
 def err_odr_function_type_inconsistent : Error<
   "external function %0 declared with incompatible types in different "
   "translation units (%1 vs. %2)">;
-def warn_odr_tag_type_inconsistent : Warning<
-  "type %0 has incompatible definitions in different translation units">,
-  InGroup<DiagGroup<"odr">>;
+def warn_odr_tag_type_inconsistent
+    : Warning<"type %0 has incompatible definitions in different translation "
+              "units">,
+      InGroup<DiagGroup<"odr">>;
+def err_odr_tag_type_inconsistent
+    : Error<"type %0 has incompatible definitions in different translation "
+            "units">;
 def note_odr_tag_kind_here: Note<
   "%0 is a %select{struct|interface|union|class|enum}1 here">;
 def note_odr_field : Note<"field %0 has type %1 here">;
+def note_odr_field_name : Note<"field has name %0 here">;
 def note_odr_missing_field : Note<"no corresponding field here">;
 def note_odr_bit_field : Note<"bit-field %0 with type %1 and length %2 here">;
 def note_odr_not_bit_field : Note<"field %0 is not a bit-field">;

clang/include/clang/Sema/Sema.h

@@ -1542,6 +1542,10 @@ class Sema {
 
   bool hasVisibleMergedDefinition(NamedDecl *Def);
 
+  /// Determine if \p D and \p Suggested have a structurally compatible
+  /// layout as described in C11 6.2.7/1.
+  bool hasStructuralCompatLayout(Decl *D, Decl *Suggested);
+
   /// Determine if \p D has a visible definition. If not, suggest a declaration
   /// that should be made visible to expose the definition.
   bool hasVisibleDefinition(NamedDecl *D, NamedDecl **Suggested,
@@ -1629,9 +1633,13 @@ class Sema {
   //
 
   struct SkipBodyInfo {
-    SkipBodyInfo() : ShouldSkip(false), Previous(nullptr) {}
+    SkipBodyInfo()
+        : ShouldSkip(false), CheckSameAsPrevious(false), Previous(nullptr),
+          New(nullptr) {}
     bool ShouldSkip;
+    bool CheckSameAsPrevious;
     NamedDecl *Previous;
+    NamedDecl *New;
   };
 
   DeclGroupPtrTy ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType = nullptr);
@@ -2145,13 +2153,11 @@ class Sema {
   };
 
   Decl *ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK,
-                 SourceLocation KWLoc, CXXScopeSpec &SS,
-                 IdentifierInfo *Name, SourceLocation NameLoc,
-                 AttributeList *Attr, AccessSpecifier AS,
-                 SourceLocation ModulePrivateLoc,
-                 MultiTemplateParamsArg TemplateParameterLists,
-                 bool &OwnedDecl, bool &IsDependent,
-                 SourceLocation ScopedEnumKWLoc,
+                 SourceLocation KWLoc, CXXScopeSpec &SS, IdentifierInfo *Name,
+                 SourceLocation NameLoc, AttributeList *Attr,
+                 AccessSpecifier AS, SourceLocation ModulePrivateLoc,
+                 MultiTemplateParamsArg TemplateParameterLists, bool &OwnedDecl,
+                 bool &IsDependent, SourceLocation ScopedEnumKWLoc,
                  bool ScopedEnumUsesClassTag, TypeResult UnderlyingType,
                  bool IsTypeSpecifier, bool IsTemplateParamOrArg,
                  SkipBodyInfo *SkipBody = nullptr);
@@ -2219,6 +2225,12 @@ class Sema {
   /// struct, or union).
   void ActOnTagStartDefinition(Scope *S, Decl *TagDecl);
 
+  /// Perform ODR-like check for C/ObjC when merging tag types from modules.
+  /// Differently from C++, actually parse the body and reject / error out
+  /// in case of a structural mismatch.
+  bool ActOnDuplicateDefinition(DeclSpec &DS, Decl *Prev,
+                                SkipBodyInfo &SkipBody);
+
   typedef void *SkippedDefinitionContext;
 
   /// \brief Invoked when we enter a tag definition that we're skipping.
@@ -2272,8 +2284,8 @@ class Sema {
 
   Decl *ActOnEnumConstant(Scope *S, Decl *EnumDecl, Decl *LastEnumConstant,
                           SourceLocation IdLoc, IdentifierInfo *Id,
-                          AttributeList *Attrs,
-                          SourceLocation EqualLoc, Expr *Val);
+                          AttributeList *Attrs, SourceLocation EqualLoc,
+                          Expr *Val);
   void ActOnEnumBody(SourceLocation EnumLoc, SourceRange BraceRange,
                      Decl *EnumDecl,
                      ArrayRef<Decl *> Elements,

clang/lib/AST/ASTStructuralEquivalence.cpp

@@ -735,13 +735,28 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
   // Check for equivalent field names.
   IdentifierInfo *Name1 = Field1->getIdentifier();
   IdentifierInfo *Name2 = Field2->getIdentifier();
-  if (!::IsStructurallyEquivalent(Name1, Name2))
+  if (!::IsStructurallyEquivalent(Name1, Name2)) {
+    if (Context.Complain) {
+      Context.Diag2(Owner2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
+          << Context.ToCtx.getTypeDeclType(Owner2);
+      Context.Diag2(Field2->getLocation(), diag::note_odr_field_name)
+          << Field2->getDeclName();
+      Context.Diag1(Field1->getLocation(), diag::note_odr_field_name)
+          << Field1->getDeclName();
+    }
     return false;
+  }
 
   if (!IsStructurallyEquivalent(Context, Field1->getType(),
                                 Field2->getType())) {
     if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(Owner2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
           << Context.ToCtx.getTypeDeclType(Owner2);
       Context.Diag2(Field2->getLocation(), diag::note_odr_field)
           << Field2->getDeclName() << Field2->getType();
@@ -753,7 +768,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 
   if (Field1->isBitField() != Field2->isBitField()) {
     if (Context.Complain) {
-      Context.Diag2(Owner2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(Owner2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
           << Context.ToCtx.getTypeDeclType(Owner2);
       if (Field1->isBitField()) {
         Context.Diag1(Field1->getLocation(), diag::note_odr_bit_field)
@@ -780,7 +798,9 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     if (Bits1 != Bits2) {
       if (Context.Complain) {
         Context.Diag2(Owner2->getLocation(),
-                      diag::warn_odr_tag_type_inconsistent)
+                      Context.ErrorOnTagTypeMismatch
+                          ? diag::err_odr_tag_type_inconsistent
+                          : diag::warn_odr_tag_type_inconsistent)
             << Context.ToCtx.getTypeDeclType(Owner2);
         Context.Diag2(Field2->getLocation(), diag::note_odr_bit_field)
             << Field2->getDeclName() << Field2->getType() << Bits2;
@@ -799,7 +819,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
                                      RecordDecl *D1, RecordDecl *D2) {
   if (D1->isUnion() != D2->isUnion()) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag1(D1->getLocation(), diag::note_odr_tag_kind_here)
           << D1->getDeclName() << (unsigned)D1->getTagKind();
@@ -927,7 +950,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
        Field1 != Field1End; ++Field1, ++Field2) {
     if (Field2 == Field2End) {
       if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+        Context.Diag2(D2->getLocation(),
+                      Context.ErrorOnTagTypeMismatch
+                          ? diag::err_odr_tag_type_inconsistent
+                          : diag::warn_odr_tag_type_inconsistent)
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag1(Field1->getLocation(), diag::note_odr_field)
             << Field1->getDeclName() << Field1->getType();
@@ -942,7 +968,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 
   if (Field2 != Field2End) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag2(Field2->getLocation(), diag::note_odr_field)
           << Field2->getDeclName() << Field2->getType();
@@ -964,7 +993,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
        EC1 != EC1End; ++EC1, ++EC2) {
     if (EC2 == EC2End) {
       if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+        Context.Diag2(D2->getLocation(),
+                      Context.ErrorOnTagTypeMismatch
+                          ? diag::err_odr_tag_type_inconsistent
+                          : diag::warn_odr_tag_type_inconsistent)
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag1(EC1->getLocation(), diag::note_odr_enumerator)
             << EC1->getDeclName() << EC1->getInitVal().toString(10);
@@ -978,7 +1010,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     if (!llvm::APSInt::isSameValue(Val1, Val2) ||
         !IsStructurallyEquivalent(EC1->getIdentifier(), EC2->getIdentifier())) {
       if (Context.Complain) {
-        Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+        Context.Diag2(D2->getLocation(),
+                      Context.ErrorOnTagTypeMismatch
+                          ? diag::err_odr_tag_type_inconsistent
+                          : diag::warn_odr_tag_type_inconsistent)
             << Context.ToCtx.getTypeDeclType(D2);
         Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
             << EC2->getDeclName() << EC2->getInitVal().toString(10);
@@ -991,7 +1026,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
 
   if (EC2 != EC2End) {
     if (Context.Complain) {
-      Context.Diag2(D2->getLocation(), diag::warn_odr_tag_type_inconsistent)
+      Context.Diag2(D2->getLocation(),
+                    Context.ErrorOnTagTypeMismatch
+                        ? diag::err_odr_tag_type_inconsistent
+                        : diag::warn_odr_tag_type_inconsistent)
           << Context.ToCtx.getTypeDeclType(D2);
       Context.Diag2(EC2->getLocation(), diag::note_odr_enumerator)
           << EC2->getDeclName() << EC2->getInitVal().toString(10);

clang/lib/Parse/ParseDecl.cpp

@@ -4319,8 +4319,15 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
     return;
   }
 
-  if (Tok.is(tok::l_brace) && TUK != Sema::TUK_Reference)
-    ParseEnumBody(StartLoc, TagDecl);
+  if (Tok.is(tok::l_brace) && TUK != Sema::TUK_Reference) {
+    Decl *D = SkipBody.CheckSameAsPrevious ? SkipBody.New : TagDecl;
+    ParseEnumBody(StartLoc, D);
+    if (SkipBody.CheckSameAsPrevious &&
+        !Actions.ActOnDuplicateDefinition(DS, TagDecl, SkipBody)) {
+      DS.SetTypeSpecError();
+      return;
+    }
+  }
 
   if (DS.SetTypeSpecType(DeclSpec::TST_enum, StartLoc,
                          NameLoc.isValid() ? NameLoc : StartLoc,
@@ -4392,11 +4399,9 @@ void Parser::ParseEnumBody(SourceLocation StartLoc, Decl *EnumDecl) {
     }
 
     // Install the enumerator constant into EnumDecl.
-    Decl *EnumConstDecl = Actions.ActOnEnumConstant(getCurScope(), EnumDecl,
-                                                    LastEnumConstDecl,
-                                                    IdentLoc, Ident,
-                                                    attrs.getList(), EqualLoc,
-                                                    AssignedVal.get());
+    Decl *EnumConstDecl = Actions.ActOnEnumConstant(
+        getCurScope(), EnumDecl, LastEnumConstDecl, IdentLoc, Ident,
+        attrs.getList(), EqualLoc, AssignedVal.get());
     EnumAvailabilityDiags.back().done();
 
     EnumConstantDecls.push_back(EnumConstDecl);

clang/lib/Parse/ParseDeclCXX.cpp

@@ -1910,8 +1910,18 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
     else if (getLangOpts().CPlusPlus)
       ParseCXXMemberSpecification(StartLoc, AttrFixitLoc, attrs, TagType,
                                   TagOrTempResult.get());
-    else
-      ParseStructUnionBody(StartLoc, TagType, TagOrTempResult.get());
+    else {
+      Decl *D =
+          SkipBody.CheckSameAsPrevious ? SkipBody.New : TagOrTempResult.get();
+      // Parse the definition body.
+      ParseStructUnionBody(StartLoc, TagType, D);
+      if (SkipBody.CheckSameAsPrevious &&
+          !Actions.ActOnDuplicateDefinition(DS, TagOrTempResult.get(),
+                                            SkipBody)) {
+        DS.SetTypeSpecError();
+        return;
+      }
+    }
   }
 
   if (!TagOrTempResult.isInvalid())