[PATCH] avoid erroneous argument types when checking built-in signatures (PR c/96596)

[Martin Sebor via Gcc-patches]

The attached change has match_builtin_function_types() fail
for erroneous argument types to prevent an ICE due to assuming
they are necessarily valid.

Martin

PR c/96596 - ICE in match_builtin_function_types on a declaration of a built-in with invalid array argument

gcc/c/ChangeLog:

	PR c/96596
	* c-decl.c (match_builtin_function_types): Avoid dealing with erroneous
	argument type.

gcc/testsuite/ChangeLog:

	PR c/96596
	* gcc.dg/Wbuiltin-declaration-mismatch-16.c: New test.

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 5d6b504fe78..190c00bd435 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -1712,7 +1712,10 @@ match_builtin_function_types (tree newtype, tree oldtype,
 	return NULL_TREE;
 
       tree oldtype = TYPE_MAIN_VARIANT (TREE_VALUE (oldargs));
-      tree newtype = TYPE_MAIN_VARIANT (TREE_VALUE (newargs));
+      tree newtype = TREE_VALUE (newargs);
+      if (newtype == error_mark_node)
+       return NULL_TREE;
+      newtype = TYPE_MAIN_VARIANT (newtype);
 
       if (!types_close_enough_to_match (oldtype, newtype))
 	return NULL_TREE;
diff --git a/gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-16.c b/gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-16.c
new file mode 100644
index 00000000000..494fff9ec60
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-16.c
@@ -0,0 +1,12 @@
+/* PR c/96596 - ICE on a declaration of a built-in with invalid array
+   argument
+   { dg-do compile } */
+
+void __builtin_abort (int[foo]);            /* { dg-error "'foo' undeclared" } */
+void __builtin_trap (int[__SIZE_MAX__]);    /* { dg-error "size of unnamed array is too large" } */
+void __builtin_unreachable (int[][]);       /* { dg-error "array type has incomplete element type" } */
+
+void __builtin_exit (int, int[+]);          /* { dg-error "expected expression before" } */
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch" }  */
+