https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116895
--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Hans-Peter Nilsson <h...@gcc.gnu.org>: https://gcc.gnu.org/g:b1696ffd46872907b324996d4cdf28a2b9df209d commit r15-3982-gb1696ffd46872907b324996d4cdf28a2b9df209d Author: Hans-Peter Nilsson <h...@axis.com> Date: Sun Sep 29 05:47:03 2024 +0200 libstdc++-v3: Fix signed-overflow warning for newlib/ctype_base.h, PR116895 There are 100+ regressions when running the g++ testsuite for newlib targets (probably excepting ARM-based ones) e.g cris-elf after commit r15-3859-g63a598deb0c9fc "libstdc++: #ifdef out #pragma GCC system_header", which effectively no longer silences warnings for gcc-installed system headers. Some of these regressions are fixed by r15-3928. For the remaining ones, there's in g++.log: FAIL: g++.old-deja/g++.robertl/eb79.C -std=c++26 (test for excess errors) Excess errors: /gccobj/cris-elf/libstdc++-v3/include/cris-elf/bits/ctype_base.h:50:53: \ warning: overflow in conversion from 'int' to 'std::ctype_base::mask' \ {aka 'char'} changes value from '151' to '-105' [-Woverflow] This is because the _B macro in newlib's ctype.h (from where the "_<letter>" macros come) is bit 7, the sign-bit of 8-bit types: #define _B 0200 Using it in an int-expression that is then truncated to 8 bits will "change" the value to negative for a default-signed char. If this code was created from scratch, it should have been an unsigned type, however it's not advisable to change the type of mask as this affects the API. The least ugly option seems to be to silence the warning by explict casts in the initializer, and for consistency, doing it for all members. PR libstdc++/116895 * config/os/newlib/ctype_base.h: Avoid signed-overflow warnings by explicitly casting initializer expressions to mask.
