From 823685221de986afb729910a6f2237f07a377f17 Mon Sep 17 00:00:00 2001 From: Roger Sayle Date: Wed, 1 Sep 2021 08:38:39 +0100 Subject: C: PR c/79412: Poison decls with error_mark_node after type mismatch This patch fixes an ICE during error-recovery regression in the C front-end. The symptom is that the middle-end's sanity checking assertions fail during gimplification when being asked to increment an array, which is non-sense. The issue is that the C-front end has detected the type mismatch and reported an error to the user, but hasn't provided any indication of this to the middle-end, simply passing bogus trees that the optimizers recognize as invalid. This appears to be a frequently reported ICE with 94730, 94731, 101036 and 101365 all marked as duplicates. I believe the correct (polite) fix is to mark the mismatched types as problematic/dubious in the front-end, when the error is spotted, so that the middle-end has a heads-up and can be a little more forgiving. This patch to c-decl.c's duplicate_decls sets (both) mismatched types to error_mark_node if they are significantly different, and we've issued an error message. Alas, this is too punitive for FUNCTION_DECLs where we store return types, parameter lists, parameter types and attributes in the type, but fortunately the middle-end is already more cautious about trusting possibly suspect function types. This fix required one minor change to the testsuite, typedef-var-2.c where after conflicting type definitions, we now no longer assume that the (first or) second definition is the correct one. This change only affects the behaviour after seen_error(), so should be relatively safe. 2021-09-01 Roger Sayle Joseph Myers gcc/c/ChangeLog PR c/79412 * c-decl.c (duplicate_decls): On significant mismatches, mark the types of both (non-function) decls as error_mark_node, so that the middle-end can see the code is malformed. (free_attr_access_data): Don't process if the type has been set to error_mark_node. gcc/testsuite/ChangeLog PR c/79412 * gcc.dg/pr79412.c: New test case. * gcc.dg/typedef-var-2.c: Update expeted errors. --- gcc/c/c-decl.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'gcc/c/c-decl.c') diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c index 221a67f..3482d82 100644 --- a/gcc/c/c-decl.c +++ b/gcc/c/c-decl.c @@ -2957,6 +2957,17 @@ duplicate_decls (tree newdecl, tree olddecl) { /* Avoid `unused variable' and other warnings for OLDDECL. */ suppress_warning (olddecl, OPT_Wunused); + /* If the types are completely different, poison them both with + error_mark_node. */ + if (TREE_CODE (TREE_TYPE (newdecl)) != TREE_CODE (TREE_TYPE (olddecl)) + && olddecl != error_mark_node + && seen_error ()) + { + if (TREE_CODE (olddecl) != FUNCTION_DECL) + TREE_TYPE (olddecl) = error_mark_node; + if (TREE_CODE (newdecl) != FUNCTION_DECL) + TREE_TYPE (newdecl) = error_mark_node; + } return false; } @@ -12209,7 +12220,7 @@ free_attr_access_data () attr_access::free_lang_data (attrs); tree fntype = TREE_TYPE (n->decl); - if (!fntype) + if (!fntype || fntype == error_mark_node) continue; tree attrs = TYPE_ATTRIBUTES (fntype); if (!attrs) -- cgit v1.1