https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91416
--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:a809d8a737da1ccebcd93065fc57fc0f4d94894a commit r11-7975-ga809d8a737da1ccebcd93065fc57fc0f4d94894a Author: Marek Polacek <pola...@redhat.com> Date: Fri Apr 2 17:11:32 2021 -0400 c++: GC during late parsing collects live data [PR91416] Coming back to <https://gcc.gnu.org/pipermail/gcc-patches/2019-August/527699.html>: This is a crash that points to a GC problem. Consider this test: __attribute__ ((unused)) struct S { S() { } } s; We're parsing a simple-declaration. While parsing the decl specs, we parse the attribute, which means creating a TREE_LIST using ggc_alloc_*. A function body is a complete-class context so when parsing the member-specification of this class-specifier, we parse the bodies of the functions we'd queued in cp_parser_late_parsing_for_member. This then leads to this call chain: cp_parser_function_definition_after_declarator -> expand_or_defer_fn -> expand_or_defer_fn_1 -> maybe_clone_body -> expand_or_defer_fn -> cgraph_node::finalize_function -> ggc_collect. In this test, the ggc_collect call collects the TREE_LIST we had allocated, and a crash duly ensues. I couldn't do what Richard suggested, that is, attach the attribute list to struct S, because we don't pass decl_specs from cp_parser_type_specifier down to cp_parser_class_specifier. Therefore I've attempted to do "push the decl_specifiers onto a vec that is a GC root", except I couldn't really push the decl_specifiers, because first I'd have to mark cp_decl_specifier_seq with GTY(()) and even that wouldn't be enough for me to be able to create static GTY(()) vec<cp_decl_specifier_seq *, va_gc> But here we only care about cp_decl_specifier_seq::attributes, so the patch is just this. I've also extended the test so now we test a nested class too. gcc/cp/ChangeLog: PR c++/91416 * parser.c: Create a GC root for attributes in a decl specifier. (cp_parser_type_specifier): Push/pop ->attributes onto/from it. gcc/testsuite/ChangeLog: PR c++/91416 * g++.dg/other/gc7.C: New test.
