[Bug c/96596] [11 Regression] ICE: tree check: expected class ‘type’, have ‘exceptional’ (error_mark) in match_builtin_function_types

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96596

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The following change avoids the ICE:

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index b31d99fcfaf..0d2a95f63d5 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;

The code above was introduced in r268348 but the ICE predates it.