allow the format attribute to be specified in function pointer prototypes

# this is my first commit here, so please be gentle :)

llvm-svn: 48807

2 files changed, 27 insertions, 8 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index eea285cf41a..e9922dfdf99 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -2136,6 +2136,24 @@ void Sema::HandleNothrowAttribute(Decl *d, AttributeList *rawAttr) {
   d->addAttr(new NoThrowAttr());
 }
 
+static const FunctionTypeProto *getFunctionProto(Decl *d) {
+  ValueDecl *decl = dyn_cast<ValueDecl>(d);
+  if (!decl) return 0;
+
+  QualType Ty = decl->getType();
+
+  if (Ty->isFunctionPointerType()) {
+    const PointerType *PtrTy = Ty->getAsPointerType();
+    Ty = PtrTy->getPointeeType();
+  }
+
+  if (const FunctionType *FnTy = Ty->getAsFunctionType())
+    return dyn_cast<FunctionTypeProto>(FnTy->getAsFunctionType());
+
+  return 0;
+}
+
+
 /// Handle __attribute__((format(type,idx,firstarg))) attributes
 /// based on http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html
 void Sema::HandleFormatAttribute(Decl *d, AttributeList *rawAttr) {
@@ -2152,22 +2170,20 @@ void Sema::HandleFormatAttribute(Decl *d, AttributeList *rawAttr) {
     return;
   }
 
-  FunctionDecl *Fn = dyn_cast<FunctionDecl>(d);
-  if (!Fn) {
+  // GCC ignores the format attribute on K&R style function
+  // prototypes, so we ignore it as well
+  const FunctionTypeProto *proto = getFunctionProto(d);
+
+  if (!proto) {
     Diag(rawAttr->getLoc(), diag::warn_attribute_wrong_decl_type,
            "format", "function");
     return;
   }
 
-  const FunctionTypeProto *proto =
-      dyn_cast<FunctionTypeProto>(Fn->getType()->getAsFunctionType());
-  if (!proto)
-    return;
-
   // FIXME: in C++ the implicit 'this' function parameter also counts.
   // this is needed in order to be compatible with GCC
   // the index must start in 1 and the limit is numargs+1
-  unsigned NumArgs  = Fn->getNumParams();
+  unsigned NumArgs  = proto->getNumArgs();
   unsigned FirstIdx = 1;
 
   const char *Format = rawAttr->getParameterName()->getName();
diff --git a/clang/test/Sema/format-attribute.c b/clang/test/Sema/format-attribute.c
index 0b166e3c4dc..df3e4b59591 100644
--- a/clang/test/Sema/format-attribute.c
+++ b/clang/test/Sema/format-attribute.c
@@ -14,3 +14,6 @@ void g(xpto c) __attribute__((format(printf, 1, 0))); // no-error
 
 void y(char *str) __attribute__((format(strftime, 1,0))); // no-error
 void z(char *str, int c, ...) __attribute__((format(strftime, 1,2))); // expected-error {{strftime format attribute requires 3rd parameter to be 0}}
+
+int (*f_ptr)(char*,...) __attribute__((format(printf, 1,2))); // no-error
+int (*f2_ptr)(double,...) __attribute__((format(printf, 1, 2))); // expected-error {{format argument not a string type}}