Index: gcc/gcc/cp/decl.c
===================================================================
--- gcc.orig/gcc/cp/decl.c	2010-12-23 11:16:30.063178000 +0100
+++ gcc/gcc/cp/decl.c	2010-12-23 11:18:59.781928200 +0100
@@ -1009,7 +1009,11 @@ decls_match (tree newdecl, tree olddecl)
 	    }
 #endif
 	  else
-	    types_match = compparms (p1, p2);
+	    types_match =
+	      compparms (p1, p2)
+	      && (TYPE_ATTRIBUTES (TREE_TYPE (newdecl)) == NULL_TREE
+	          || targetm.comp_type_attributes (TREE_TYPE (newdecl),
+						   TREE_TYPE (olddecl)) != 0);
 	}
       else
 	types_match = 0;
Index: gcc/gcc/testsuite/g++.dg/pr15774-1.C
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/g++.dg/pr15774-1.C	2010-12-23 11:18:59.813178200 +0100
@@ -0,0 +1,15 @@
+// { dg-do compile { target i?86-*-* } }
+// Test that an new declartion with different attributes then old one fail.
+extern void foo (int); // { dg-error "ambiguates old declaration" }
+
+void
+bar (void)
+{
+  foo (1);
+}
+
+void __attribute__((stdcall)) foo (int i) // { dg-error "new declaration" }
+{
+}
+
+
Index: gcc/gcc/testsuite/g++.dg/pr15774-2.C
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ gcc/gcc/testsuite/g++.dg/pr15774-2.C	2010-12-23 11:18:59.813178200 +0100
@@ -0,0 +1,15 @@
+// { dg-do compile { target i?86-*-* } }
+// Test that old declaration is used, if new one has no attributes.
+extern void __attribute__((stdcall)) foo (int);
+
+void
+bar (void)
+{
+  foo (1);
+}
+
+void foo (int i)
+{
+}
+
+