https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94775
--- Comment #10 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:6318fe77395fc0dd59419bc4d69cd06ac0158e54 commit r10-8071-g6318fe77395fc0dd59419bc4d69cd06ac0158e54 Author: Marek Polacek <pola...@redhat.com> Date: Wed Apr 29 15:36:35 2020 -0400 tree: Don't reuse types if TYPE_USER_ALIGN differ [PR94775] Here we trip on the TYPE_USER_ALIGN (t) assert in strip_typedefs: it gets "const d[0]" with TYPE_USER_ALIGN=0 but the result built by build_cplus_array_type is "const char[0]" with TYPE_USER_ALIGN=1. When we strip_typedefs the element of the array "const d", we see it's a typedef_variant_p, so we look at its DECL_ORIGINAL_TYPE, which is char, but we need to add the const qualifier, so we call cp_build_qualified_type -> build_qualified_type where get_qualified_type checks to see if we already have such a type by walking the variants list, which in this case is: char -> c -> const char -> const char -> d -> const d Because check_base_type only checks TYPE_ALIGN and not TYPE_USER_ALIGN, we choose the first const char, which has TYPE_USER_ALIGN set. If the element type of an array has TYPE_USER_ALIGN, the array type gets it too. So we can make check_base_type stricter. I was afraid that it might make us reuse types less often, but measuring showed that we build the same amount of types with and without the patch, while bootstrapping. PR c++/94775 * tree.c (check_base_type): Return true only if TYPE_USER_ALIGN match. (check_aligned_type): Check if TYPE_USER_ALIGN match. * g++.dg/warn/Warray-bounds-10.C: New test.
