[clang][SemaTemplate] Fix a stack use after scope

[sammccall]

clang/include/clang/AST/DeclTemplate.h

2464

Is this change just to emphasize that this constructor won't copy the contents?

clang/lib/AST/DeclTemplate.cpp

1103

just initialize to params.size already? or inline this variable

[kadircet]

• Inline Params.size()

clang/include/clang/AST/DeclTemplate.h

2464

yes and also to keep the implementation of the constructor simple.

clang/include/clang/AST/DeclTemplate.h

private:
 
   // The declaration that's a friend of this class.
   FriendUnion Friend;
 
   // Location of the 'friend' specifier.
   SourceLocation FriendLoc;
 
   FriendTemplateDecl(DeclContext *DC, SourceLocation Loc,
-                     MutableArrayRef<TemplateParameterList *> Params,
+                     TemplateParameterList **Params, unsigned NumParams,
                      FriendUnion Friend, SourceLocation FriendLoc)
-      : Decl(Decl::FriendTemplate, DC, Loc), NumParams(Params.size()),
-        Params(Params.data()), Friend(Friend), FriendLoc(FriendLoc) {}
+      : Decl(Decl::FriendTemplate, DC, Loc), NumParams(NumParams),
+        Params(Params), Friend(Friend), FriendLoc(FriendLoc) {}
 
   FriendTemplateDecl(EmptyShell Empty) : Decl(Decl::FriendTemplate, Empty) {}
 
 public:
   friend class ASTDeclReader;
 
   static FriendTemplateDecl *
   Create(ASTContext &Context, DeclContext *DC, SourceLocation Loc,

clang/lib/AST/DeclTemplate.cpp

 #include "clang/AST/TypeLoc.h"
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/LLVM.h"
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
 #include <cassert>
 #include <cstdint>
 #include <memory>
 #include <utility>

 
 void FriendTemplateDecl::anchor() {}
 
 FriendTemplateDecl *
 FriendTemplateDecl::Create(ASTContext &Context, DeclContext *DC,
                            SourceLocation L,
                            MutableArrayRef<TemplateParameterList *> Params,
                            FriendUnion Friend, SourceLocation FLoc) {
-  return new (Context, DC) FriendTemplateDecl(DC, L, Params, Friend, FLoc);
+  TemplateParameterList **TPL = nullptr;
+  if (!Params.empty()) {
+    TPL = new (Context) TemplateParameterList *[Params.size()];
+    llvm::copy(Params, TPL);
+  }
+  return new (Context, DC)
+      FriendTemplateDecl(DC, L, TPL, Params.size(), Friend, FLoc);
 }
 
 FriendTemplateDecl *FriendTemplateDecl::CreateDeserialized(ASTContext &C,
                                                            unsigned ID) {
   return new (C, ID) FriendTemplateDecl(EmptyShell());
 }
 
 //===----------------------------------------------------------------------===//

clang/test/SemaTemplate/friend-template.cpp

template <class T> struct A {
     }
   };
 
   void test() {
     A<int> b;
     foo(b); // expected-note {{in instantiation}}
   }
 }
+
+namespace StackUseAfterScope {
+template <typename T> class Bar {};
+class Foo {
+  // Make sure this doesn't crash.
+  template <> friend class Bar<int>; // expected-error {{template specialization declaration cannot be a friend}}
+  bool aux;
+};
+}