https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105774
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-12 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:20ef7d7c578dab0585d70fbea571a74e8e8d4b47 commit r12-8888-g20ef7d7c578dab0585d70fbea571a74e8e8d4b47 Author: Jakub Jelinek <ja...@redhat.com> Date: Mon Oct 24 16:25:29 2022 +0200 c++: Fix up constexpr handling of char/signed char/short pre/post inc/decrement [PR105774] signed char, char or short int pre/post inc/decrement are represented by normal {PRE,POST}_{INC,DEC}REMENT_EXPRs in the FE and only gimplification ensures that the {PLUS,MINUS}_EXPR is done in unsigned version of those types: case PREINCREMENT_EXPR: case PREDECREMENT_EXPR: case POSTINCREMENT_EXPR: case POSTDECREMENT_EXPR: { tree type = TREE_TYPE (TREE_OPERAND (*expr_p, 0)); if (INTEGRAL_TYPE_P (type) && c_promoting_integer_type_p (type)) { if (!TYPE_OVERFLOW_WRAPS (type)) type = unsigned_type_for (type); return gimplify_self_mod_expr (expr_p, pre_p, post_p, 1, type); } break; } This means during constant evaluation we need to do it similarly (either using unsigned_type_for or using widening to integer_type_node). The following patch does the latter. 2022-10-24 Jakub Jelinek <ja...@redhat.com> PR c++/105774 * constexpr.cc (cxx_eval_increment_expression): For signed types that promote to int, evaluate PLUS_EXPR or MINUS_EXPR in int type. * g++.dg/cpp1y/constexpr-105774.C: New test. (cherry picked from commit da8c362c4c18cff2f2dfd5c4706bdda7576899a4)
