[PATCH] Fix crash in cleanup attr handling

[Alp Toker]

Reduction:

void c3(int *a) {
  void c3() {}
  void t3() {
    int v1 __attribute__((cleanup(c3)));
}

ResolveSingleFunctionTemplateSpecialization() returns 0 and doesn't emit
diags unless the expression has template-ids, so we must null check the
result.

Also add a better diag noting which overloads are causing the problem.

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diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index d8fef68..a02c072 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -2365,7 +2365,7 @@ def warn_cleanup_ext : Warning<
   "than a simple identifier">, 
   InGroup<GccCompat>;
 def err_attribute_cleanup_arg_not_function : Error<
-  "'cleanup' argument %select{|%1 }0is not a function">;
+  "'cleanup' argument %select{|%1 |%1 }0is not a %select{||single }0function">;
 def err_attribute_cleanup_func_must_take_one_arg : Error<
   "'cleanup' function %0 must take 1 parameter">;
 def err_attribute_cleanup_func_arg_incompatible_type : Error<
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index 3eabf87..d38d619 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -2899,10 +2899,14 @@ static void handleCleanupAttr(Sema &S, Decl *D, const AttributeList &Attr) {
   } else if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
     if (ULE->hasExplicitTemplateArgs())
       S.Diag(Loc, diag::warn_cleanup_ext);
-
-    // This will diagnose the case where the function cannot be found.
     FD = S.ResolveSingleFunctionTemplateSpecialization(ULE, true);
     NI = ULE->getNameInfo();
+    if (!FD) {
+      S.Diag(Loc, diag::err_attribute_cleanup_arg_not_function) << 2
+        << NI.getName();
+      S.NoteAllOverloadCandidates(ULE);
+      return;
+    }
   } else {
     S.Diag(Loc, diag::err_attribute_cleanup_arg_not_function) << 0;
     return;
diff --git a/test/SemaCXX/attr-cleanup.cpp b/test/SemaCXX/attr-cleanup.cpp
index b6c5853..764df99 100644
--- a/test/SemaCXX/attr-cleanup.cpp
+++ b/test/SemaCXX/attr-cleanup.cpp
@@ -19,3 +19,11 @@ class D : public C {
     int v1 __attribute__((cleanup(c2)));  // expected-error {{'c2' is a private member of 'C'}}
   }
 };
+
+namespace E {
+  void c3(int *a) {} // expected-note {{candidate function}}
+  void c3() {}       // expected-note {{candidate function}}
+  void t3() {
+    int v1 __attribute__((cleanup(c3))); // expected-error {{'c3' is not a single function}}
+  }
+}