https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116369
--- Comment #11 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:a35dd276cbf6236e08bcf6e56e62c2be41cf6e3c commit r15-3127-ga35dd276cbf6236e08bcf6e56e62c2be41cf6e3c Author: Jonathan Wakely <jwak...@redhat.com> Date: Wed Aug 21 12:29:32 2024 +0100 libstdc++: Make debug sequence members mutable [PR116369] We need to be able to attach debug mode iterators to const containers, so the safe iterator constructor uses const_cast to get a modifiable pointer to the container. If the container was defined as const, that const_cast to access its members results in undefined behaviour. PR 116369 shows a case where it results in a segfault because the container is in a rodata section (which shouldn't have happened, but the undefined behaviour in the library still exists in any case). This makes the _M_iterators and _M_const_iterators data members mutable, so that it's safe to modify them even if the declared type of the container is a const type. Ideally we would not need the const_cast at all. Instead, the _M_attach member (and everything it calls) should be const-qualified. That would work fine now, because the members that it ends up modifying are mutable. Making that change would require a number of new exports from the shared library, and would require retaining the old non-const member functions (maybe as symbol aliases) for backwards compatibility. That might be worth changing at some point, but isn't done here. libstdc++-v3/ChangeLog: PR c++/116369 * include/debug/safe_base.h (_Safe_sequence_base::_M_iterators): Add mutable specifier. (_Safe_sequence_base::_M_const_iterators): Likewise.
