Don't crash on `struct ::, struct ::` (and the same for enums).

The first part of that line doesn't parse correctly and ParseClassSpecifier() for
some reason skips to tok::comma to recover, and then
ParseDeclarationSpecifiers() sees the next struct and calls
ParseClassSpecifier() again with the same DeclSpec object.

However, the first call already called ActOnCXXGlobalScopeSpecifier() on the
DeclSpec's CXXScopeSpec, and sema gets confused when this gets called again.

As a fix, let ParseClassSpecifier() (and ParseEnumSpecifier()) call
ParseOptionalCXXScopeSpec() with a temporary CXXScopeSpec object, and only
copy it into the DeclSpec if things work out.  (This is also how all the other
functions that set the DeclSpec's TypeSpecScope set it.)

Found by SLi's bot.

llvm-svn: 229288

3 files changed, 25 insertions, 6 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index 8fcfcb34be2..a17fd6dbee8 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -3648,11 +3648,12 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
     // if a fixed underlying type is allowed.
     ColonProtectionRAIIObject X(*this, AllowFixedUnderlyingType);
 
-    if (ParseOptionalCXXScopeSpecifier(SS, ParsedType(),
+    CXXScopeSpec Spec;
+    if (ParseOptionalCXXScopeSpecifier(Spec, ParsedType(),
                                        /*EnteringContext=*/true))
       return;
 
-    if (SS.isSet() && Tok.isNot(tok::identifier)) {
+    if (Spec.isSet() && Tok.isNot(tok::identifier)) {
       Diag(Tok, diag::err_expected) << tok::identifier;
       if (Tok.isNot(tok::l_brace)) {
         // Has no name and is not a definition.
@@ -3661,6 +3662,8 @@ void Parser::ParseEnumSpecifier(SourceLocation StartLoc, DeclSpec &DS,
         return;
       }
     }
+
+    SS = Spec;
   }
 
   // Must have either 'enum name' or 'enum {...}'.
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 63baaefc2fc..0a88d202b8b 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1310,11 +1310,19 @@ void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
     // is a base-specifier-list.
     ColonProtectionRAIIObject X(*this);
 
-    if (ParseOptionalCXXScopeSpecifier(SS, ParsedType(), EnteringContext))
+    CXXScopeSpec Spec;
+    bool HasValidSpec = true;
+    if (ParseOptionalCXXScopeSpecifier(Spec, ParsedType(), EnteringContext)) {
       DS.SetTypeSpecError();
-    if (SS.isSet())
-      if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id))
+      HasValidSpec = false;
+    }
+    if (Spec.isSet())
+      if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id)) {
         Diag(Tok, diag::err_expected) << tok::identifier;
+        HasValidSpec = false;
+      }
+    if (HasValidSpec)
+      SS = Spec;
   }
 
   TemplateParameterLists *TemplateParams = TemplateInfo.TemplateParams;
diff --git a/clang/test/Parser/recovery.cpp b/clang/test/Parser/recovery.cpp
index e53a361dca8..bca9ace89e2 100644
--- a/clang/test/Parser/recovery.cpp
+++ b/clang/test/Parser/recovery.cpp
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -verify -std=c++11 %s
+// RUN: %clang_cc1 -verify -std=c++11 -fms-extensions %s
 
 8gi///===--- recovery.cpp ---===// // expected-error {{unqualified-id}}
 namespace Std { // expected-note {{here}}
@@ -202,3 +202,11 @@ namespace pr15133 {
   struct S2 :: S3 :: public S2 {  // expected-error{{'public' cannot be a part of nested name specifier; did you mean ':'?}}
   };
 }
+
+namespace InvalidEmptyNames {
+// These shouldn't crash, the diagnostics aren't important.
+struct ::, struct ::; // expected-error 2 {{expected identifier}} expected-error 2 {{declaration of anonymous struct must be a definition}} expected-warning {{declaration does not declare anything}}
+enum ::, enum ::; // expected-error 2 {{expected identifier}} expected-warning {{declaration does not declare anything}}
+struct ::__super, struct ::__super; // expected-error 2 {{expected identifier}} expected-error 2 {{expected '::' after '__super'}}
+struct ::template foo, struct ::template bar; // expected-error 2 {{expected identifier}} expected-error 2 {{declaration of anonymous struct must be a definition}} expected-warning {{declaration does not declare anything}}
+}