https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79412
--- Comment #16 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:823685221de986afb729910a6f2237f07a377f17 commit r12-3278-g823685221de986afb729910a6f2237f07a377f17 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Wed Sep 1 08:38:39 2021 +0100 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 <ro...@nextmovesoftware.com> Joseph Myers <jos...@codesourcery.com> 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.
