https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-14 branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:4896bb3199253dc350f8fb5ff63370310ca27ce2 commit r14-10232-g4896bb3199253dc350f8fb5ff63370310ca27ce2 Author: Jonathan Wakely <jwak...@redhat.com> Date: Fri May 17 10:55:32 2024 +0100 libstdc++: Implement std::formatter<std::thread::id> without <sstream> [PR115099] The std::thread::id formatter uses std::basic_ostringstream without including <sstream>, which went unnoticed because the test for it uses a stringstream to check the output is correct. The fix implemented here is to stop using basic_ostringstream for formatting thread::id and just use std::format instead. As a drive-by fix, the formatter specialization is constrained to require that the thread::id::native_handle_type can be formatted, to avoid making the formatter ill-formed if the pthread_t type is not a pointer or integer. Since non-void pointers can't be formatted, ensure that we convert pointers to const void* for formatting. Make a similar change to the existing operator<< overload so that in the unlikely case that pthread_t is a typedef for char* we don't treat it as a null-terminated string when inserting into a stream. libstdc++-v3/ChangeLog: PR libstdc++/115099 * include/bits/std_thread.h: Declare formatter as friend of thread::id. * include/std/thread (operator<<): Convert non-void pointers to void pointers for output. (formatter): Add constraint that thread::native_handle_type is a pointer or integer. (formatter::format): Reimplement without basic_ostringstream. * testsuite/30_threads/thread/id/output.cc: Check output compiles before <sstream> has been included. (cherry picked from commit 1a5e4dd83788ea4c049d354d83ad58a6a3d747e6)
