diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index c0e247b..df44faa 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -7418,6 +7418,8 @@ check_user_alignment (const_tree align, bool allow_zero)
 {
   int i;
 
+  if (error_operand_p (align))
+    return -1;
   if (TREE_CODE (align) != INTEGER_CST
       || !INTEGRAL_TYPE_P (TREE_TYPE (align)))
     {
@@ -7539,7 +7541,8 @@ handle_aligned_attribute (tree *node, tree ARG_UNUSED (name), tree args,
   if (args)
     {
       align_expr = TREE_VALUE (args);
-      if (align_expr && TREE_CODE (align_expr) != IDENTIFIER_NODE)
+      if (align_expr && TREE_CODE (align_expr) != IDENTIFIER_NODE
+	  && TREE_CODE (align_expr) != FUNCTION_DECL)
 	align_expr = default_conversion (align_expr);
     }
   else
@@ -8404,9 +8407,11 @@ handle_tm_wrap_attribute (tree *node, tree name, tree args,
   else
     {
       tree wrap_decl = TREE_VALUE (args);
-      if (TREE_CODE (wrap_decl) != IDENTIFIER_NODE
-	  && TREE_CODE (wrap_decl) != VAR_DECL
-	  && TREE_CODE (wrap_decl) != FUNCTION_DECL)
+      if (error_operand_p (wrap_decl))
+        ;
+      else if (TREE_CODE (wrap_decl) != IDENTIFIER_NODE
+	       && TREE_CODE (wrap_decl) != VAR_DECL
+	       && TREE_CODE (wrap_decl) != FUNCTION_DECL)
 	error ("%qE argument not an identifier", name);
       else
 	{
@@ -8533,7 +8538,8 @@ handle_vector_size_attribute (tree *node, tree name, tree args,
   *no_add_attrs = true;
 
   size = TREE_VALUE (args);
-  if (size && TREE_CODE (size) != IDENTIFIER_NODE)
+  if (size && TREE_CODE (size) != IDENTIFIER_NODE
+      && TREE_CODE (size) != FUNCTION_DECL)
     size = default_conversion (size);
 
   if (!tree_fits_uhwi_p (size))
@@ -8944,8 +8950,12 @@ handle_sentinel_attribute (tree *node, tree name, tree args,
   if (args)
     {
       tree position = TREE_VALUE (args);
+      if (position && TREE_CODE (position) != IDENTIFIER_NODE
+	  && TREE_CODE (position) != FUNCTION_DECL)
+	position = default_conversion (position);
 
-      if (TREE_CODE (position) != INTEGER_CST)
+      if (TREE_CODE (position) != INTEGER_CST
+          || !INTEGRAL_TYPE_P (TREE_TYPE (position)))
 	{
 	  warning (OPT_Wattributes,
 		   "requested position is not an integer constant");
diff --git gcc/c/c-parser.c gcc/c/c-parser.c
index 5653e49..8d91d6b 100644
--- gcc/c/c-parser.c
+++ gcc/c/c-parser.c
@@ -3943,11 +3943,16 @@ c_parser_attributes (c_parser *parser)
 	     In objective-c the identifier may be a classname.  */
 	  if (c_parser_next_token_is (parser, CPP_NAME)
 	      && (c_parser_peek_token (parser)->id_kind == C_ID_ID
-		  || (c_dialect_objc () 
-		      && c_parser_peek_token (parser)->id_kind == C_ID_CLASSNAME))
+		  || (c_dialect_objc ()
+		      && c_parser_peek_token (parser)->id_kind
+			 == C_ID_CLASSNAME))
 	      && ((c_parser_peek_2nd_token (parser)->type == CPP_COMMA)
 		  || (c_parser_peek_2nd_token (parser)->type
-		      == CPP_CLOSE_PAREN)))
+		      == CPP_CLOSE_PAREN))
+	      && (attribute_takes_identifier_p (attr_name)
+		  || (c_dialect_objc ()
+		      && c_parser_peek_token (parser)->id_kind
+			 == C_ID_CLASSNAME)))
 	    {
 	      tree arg1 = c_parser_peek_token (parser)->value;
 	      c_parser_consume_token (parser);
diff --git gcc/testsuite/c-c++-common/attributes-1.c gcc/testsuite/c-c++-common/attributes-1.c
index af4dd12..8458e47 100644
--- gcc/testsuite/c-c++-common/attributes-1.c
+++ gcc/testsuite/c-c++-common/attributes-1.c
@@ -9,7 +9,7 @@ typedef char vec __attribute__((vector_size(bar))); /* { dg-warning "ignored" }
 void f1(char*) __attribute__((nonnull(bar))); /* { dg-error "invalid operand" } */
 void f2(char*) __attribute__((nonnull(1,bar))); /* { dg-error "invalid operand" } */
 
-void g() __attribute__((aligned(bar))); /* { dg-error "invalid value|not an integer" } */
+void g() __attribute__((aligned(bar)));
 
 void foo(void);
 void* my_calloc(unsigned, unsigned) __attribute__((alloc_size(1,foo))); /* { dg-warning "outside range" } */
diff --git gcc/testsuite/c-c++-common/pr50459.c gcc/testsuite/c-c++-common/pr50459.c
index e69de29..f837b63 100644
--- gcc/testsuite/c-c++-common/pr50459.c
+++ gcc/testsuite/c-c++-common/pr50459.c
@@ -0,0 +1,14 @@
+/* PR c/50459 */
+/* { dg-do compile } */
+/* { dg-options "-Wall -Wextra" } */
+
+enum { A = 128, B = 1 };
+void *fn1 (void) __attribute__((assume_aligned (A)));
+void *fn2 (void) __attribute__((assume_aligned (A, 4)));
+void fn3 (void) __attribute__((constructor (A)));
+void fn4 (void) __attribute__((destructor (A)));
+void *fn5 (int) __attribute__((alloc_size (B)));
+void *fn6 (int) __attribute__((alloc_align (B)));
+void fn7 (const char *, ...) __attribute__ ((sentinel (B)));
+int __attribute__((vector_size (A))) a;
+int __attribute__((aligned (A))) foo;
diff --git gcc/testsuite/c-c++-common/pr59280.c gcc/testsuite/c-c++-common/pr59280.c
index 779f0fb..581a1cf 100644
--- gcc/testsuite/c-c++-common/pr59280.c
+++ gcc/testsuite/c-c++-common/pr59280.c
@@ -1,4 +1,4 @@
 /* PR c/59280 */
 /* { dg-do compile } */
 
-void bar (char *) __attribute__((constructor(foo))); /* { dg-error "constructor priorities must be integers|was not declared|constructor priorities are not supported" } */
+void bar (char *) __attribute__((constructor(foo))); /* { dg-error "constructor priorities must be integers|was not declared|undeclared|constructor priorities are not supported" } */
diff --git gcc/testsuite/gcc.dg/nonnull-2.c gcc/testsuite/gcc.dg/nonnull-2.c
index bd36d232..d570a46 100644
--- gcc/testsuite/gcc.dg/nonnull-2.c
+++ gcc/testsuite/gcc.dg/nonnull-2.c
@@ -6,7 +6,7 @@ extern void func1 () __attribute__((nonnull)); /* { dg-error "without arguments"
 
 extern void func2 (char *) __attribute__((nonnull(2))); /* { dg-error "out-of-range operand" } */
 
-extern void func3 (char *) __attribute__((nonnull(foo))); /* { dg-error "invalid operand number" } */
+extern void func3 (char *) __attribute__((nonnull(foo))); /* { dg-error "invalid operand number|undeclared" } */
 
 extern void func4 (int) __attribute__((nonnull(1))); /* { dg-error "references non-pointer" } */
 
diff --git gcc/testsuite/gcc.dg/pr55570.c gcc/testsuite/gcc.dg/pr55570.c
index 903bb03..5f5555e 100644
--- gcc/testsuite/gcc.dg/pr55570.c
+++ gcc/testsuite/gcc.dg/pr55570.c
@@ -1,4 +1,4 @@
 /* PR c/55570 */
 /* { dg-do compile } */
 
-char array[16] __attribute__((aligned (SOME_NOT_DEFINED_MACRO))); /* { dg-error "requested alignment is not an integer constant" } */
+char array[16] __attribute__((aligned (SOME_NOT_DEFINED_MACRO))); /* { dg-error "undeclared here" } */
diff --git gcc/testsuite/gcc.dg/tm/wrap-2.c gcc/testsuite/gcc.dg/tm/wrap-2.c
index 2948633..372d666 100644
--- gcc/testsuite/gcc.dg/tm/wrap-2.c
+++ gcc/testsuite/gcc.dg/tm/wrap-2.c
@@ -10,7 +10,7 @@ int f7(void);
 void g1(void) W(f1);
 void g2(void) W(f2);	/* { dg-error "is not compatible" } */
 void g3(void) W(i3);	/* { dg-error "is not a function" } */
-void g4(void) W(f4);	/* { dg-error "is not a function" } */
+void g4(void) W(f4);	/* { dg-error "undeclared" } */
 void g5(void) W(1);	/* { dg-error "not an identifier" } */
 void g6(void) W("f1");	/* { dg-error "not an identifier" } */
 void g7(void) W(f7);	/* { dg-error "is not compatible" } */
