4 files changed, 33 insertions, 7 deletions
diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
index a407a162774..8195fcb253c 100644
--- a/clang/include/clang/AST/DeclBase.h
+++ b/clang/include/clang/AST/DeclBase.h
@@ -279,7 +279,8 @@ public:
 
   /// \brief Whether this declaration was used, meaning that a definition
   /// is required.
-  bool isUsed() const { return Used; }
+  bool isUsed() const;
+  
   void setUsed(bool U = true) { Used = U; }
 
   /// \brief Retrieve the level of precompiled header from which this
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a37177ba344..e2912ea3517 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -88,10 +88,8 @@ def warn_decl_in_param_list : Warning<
 def err_array_star_in_function_definition : Error<
   "variable length array must be bound in function definition">;
 def warn_unused_function : Warning<"unused function %0">,
-// FIXME: Temporarily disabled pending PR6321.
-//  InGroup<UnusedFunction>, DefaultIgnore;
-  DefaultIgnore;
-
+  InGroup<UnusedFunction>, DefaultIgnore;
+  
 def warn_implicit_function_decl : Warning<
   "implicit declaration of function %0">,
   InGroup<ImplicitFunctionDeclare>, DefaultIgnore;
diff --git a/clang/lib/AST/DeclBase.cpp b/clang/lib/AST/DeclBase.cpp
index 863a1cbd03c..222adcb28e4 100644
--- a/clang/lib/AST/DeclBase.cpp
+++ b/clang/lib/AST/DeclBase.cpp
@@ -194,6 +194,24 @@ ASTContext &Decl::getASTContext() const {
   return getTranslationUnitDecl()->getASTContext();
 }
 
+bool Decl::isUsed() const { 
+  if (Used)
+    return true;
+  
+  // Check for used attribute.
+  if (hasAttr<UsedAttr>())
+    return true;
+  
+  // Check redeclarations for used attribute.
+  for (redecl_iterator I = redecls_begin(), E = redecls_end(); I != E; ++I) {
+    if (I->hasAttr<UsedAttr>() || I->Used)
+      return true;
+  }
+  
+  return false; 
+}
+
+
 unsigned Decl::getIdentifierNamespaceForKind(Kind DeclKind) {
   switch (DeclKind) {
     case Function:
diff --git a/clang/test/Sema/warn-unused-function.c b/clang/test/Sema/warn-unused-function.c
index 81ea82dd163..1a2a50e1aa0 100644
--- a/clang/test/Sema/warn-unused-function.c
+++ b/clang/test/Sema/warn-unused-function.c
@@ -1,5 +1,4 @@
 // RUN: %clang_cc1 -fsyntax-only -Wunused-function -verify %s
-// XFAIL: *
 
 void foo() {}
 static void f2() {} 
@@ -14,4 +13,14 @@ extern void f3() { } // expected-warning{{unused}}
 // FIXME: This will trigger a warning when it should not.
 // Update once PR6281 is fixed.
 //inline static void f4();
-//void f4() { } 
+//void f4() { }
+
+static void __attribute__((used)) f5() {}
+static void f6();
+static void __attribute__((used)) f6();
+static void f6() {};
+
+static void f7(void);
+void f8(void(*a0)(void));
+void f9(void) { f8(f7); }
+static void f7(void) {}