https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86274
--- Comment #10 from Martin Jambor <jamborm at gcc dot gnu.org> --- And in the previous dump (fixup_cfg1), we have <bb 3> : __len = D.127713; __builtin_va_end (&__args); std::allocator<char>::allocator (&D.122645); _1 = (sizetype) __len; _2 = __s + _1; std::__cxx11::basic_string<char>::basic_string<char*> (<retval>, __s, _2, &D.122645); So I'd say that it is either gimplification or SSA creation that does not handle this situation correctly.