[Sema] Make `&function_with_enable_if_attrs` an error

This fixes a bug where one can take the address of a conditionally
enabled function to drop its enable_if guards. For example:

  int foo(int a) __attribute__((enable_if(a > 0, "")));
  int (*p)(int) = &foo;
  int result = p(-1); // compilation succeeds; calls foo(-1)

Overloading logic has been updated to reflect this change, as well.

Functions with enable_if attributes that are always true are still
allowed to have their address taken.

Differential Revision: http://reviews.llvm.org/D13607

llvm-svn: 250090

1 files changed, 3 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 74db24f28dc..461b3b648dc 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -6599,6 +6599,8 @@ InitializationSequence::Perform(Sema &S,
 
     case SK_CAssignment: {
       QualType SourceType = CurInit.get()->getType();
+      // Save off the initial CurInit in case we need to emit a diagnostic
+      ExprResult InitialCurInit = CurInit;
       ExprResult Result = CurInit;
       Sema::AssignConvertType ConvTy =
         S.CheckSingleAssignmentConstraints(Step->Type, Result, true,
@@ -6621,7 +6623,7 @@ InitializationSequence::Perform(Sema &S,
       bool Complained;
       if (S.DiagnoseAssignmentResult(ConvTy, Kind.getLocation(),
                                      Step->Type, SourceType,
-                                     CurInit.get(),
+                                     InitialCurInit.get(),
                                      getAssignmentAction(Entity, true),
                                      &Complained)) {
         PrintInitLocationNote(S, Entity);