https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118534
--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:413985b632afb07032d3b32d992029fced187814 commit r15-7014-g413985b632afb07032d3b32d992029fced187814 Author: Jakub Jelinek <ja...@redhat.com> Date: Sat Jan 18 09:14:27 2025 +0100 c++: Fix up find_array_ctor_elt RAW_DATA_CST handling [PR118534] This is the third bug discovered today with the https://gcc.gnu.org/pipermail/gcc-patches/2025-January/673945.html hack but then turned into proper testcases where embed-24.C FAILed since introduction of optimized #embed support and the others when optimizing large C++ initializers using RAW_DATA_CST. find_array_ctor_elt already has RAW_DATA_CST support, but on the following testcases it misses one case I've missed. The CONSTRUCTORs in question went through the braced_list_to_string optimization which can turn INTEGER_CST RAW_DATA_CST INTEGER_CST into just larger RAW_DATA_CST covering even those 2 bytes around it (if they appear there in the underlying RAW_DATA_OWNER). With this optimization, RAW_DATA_CST can be the last CONSTRUCTOR_ELTS elt in a CONSTRUCTOR, either the sole one or say preceeded by some unrelated other elements. Now, if RAW_DATA_CST is the only one or if there are no RAW_DATA_CSTs earlier in CONSTRUCTOR_ELTS, we can trigger a bug in find_array_ctor_elt. It has a smart optimization for the very common case where CONSTRUCTOR_ELTS have indexes and index of the last elt is equal to CONSTRUCTOR_NELTS (ary) - 1, then obviously we know there are no RAW_DATA_CSTs before it and the indexes just go from 0 to nelts-1, so when we care about any of those earlier indexes, we can just return i; and not worry about anything. Except it uses if (i < end) return i; rather than if (i < end - 1) return i; For the latter cases, i.e. anything before the last elt, we know there are no surprises and return i; is right. But for the if (i == end - 1) case, return i; is only correct if the last elt is not RAW_DATA_CST, if it is RAW_DATA_CST, we still need to split it, which is handled by the code later in the function. So, for that we need begin = end - 1, so that the binary search will just care about that last element. 2025-01-18 Jakub Jelinek <ja...@redhat.com> PR c++/118534 * constexpr.cc (find_array_ctor_elt): Don't return i early if i == end - 1 and the last elt's value is RAW_DATA_CST. * g++.dg/cpp/embed-24.C: New test. * g++.dg/cpp1y/pr118534.C: New test.
