[Bug libstdc++/115099] New: compilation error: format thread::id

[Bug libstdc++/115099] New: compilation error: format thread::id

[faithandbrave at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099

            Bug ID: 115099
           Summary: compilation error: format thread::id
           Product: gcc
           Version: 14.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: faithandbrave at gmail dot com
  Target Milestone: ---

#include <iostream>
#include <format>
#include <thread>

int main()
{
    std::cout << __cpp_lib_formatters << std::endl;
    std::cout << std::format("{}", std::this_thread::get_id()) << std::endl;
    std::cout << std::format("{: >30}", std::this_thread::get_id()) <<
std::endl;
}

outputs:

In file included from prog.cc:3:
/opt/wandbox/gcc-head/include/c++/15.0.0/thread: In instantiation of 'typename
std::basic_format_context<_Out, _CharT>::iterator
std::formatter<std::thread::id, _CharT>::format(std::thread::id,
std::basic_format_context<_Out, _CharT>&) const [with _Out =
std::__format::_Sink_iter<char>; _CharT = char; typename
std::basic_format_context<_Out, _CharT>::iterator =
std::basic_format_context<std::__format::_Sink_iter<char>, char>::iterator]':
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3247:40:   required from
'static void
std::basic_format_arg<_Context>::handle::_S_format(std::basic_format_parse_context<typename
_Context::char_type>&, _Context&, const void*) [with _Tq = const
std::thread::id; _Context =
std::basic_format_context<std::__format::_Sink_iter<char>, char>; typename
_Context::char_type = char]'
 3247 |             __format_ctx.advance_to(__f.format(__val, __format_ctx));
      |                                     ~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3255:11:   required from
'std::basic_format_arg<_Context>::handle::handle(_Tp&) [with _Tp =
std::thread::id; _Context =
std::basic_format_context<std::__format::_Sink_iter<char>, char>]'
 3255 |             auto __func = _S_format<__maybe_const_t<_Tp>>;
      |                  ^~~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3486:13:   required from
'std::basic_format_arg<_Context>::basic_format_arg(_Tp&) [with _Tp =
std::thread::id; _Context =
std::basic_format_context<std::__format::_Sink_iter<char>, char>]'
 3486 |             _M_set(static_cast<_Td>(__v));
      |                    ^~~~~~~~~~~~~~~~~~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3743:31:   required from
'static std::__format::_Arg_store<_Context, _Args>::_Element_t
std::__format::_Arg_store<_Context, _Args>::_S_make_elt(_Tp&) [with _Tp =
std::thread::id; _Context =
std::basic_format_context<std::__format::_Sink_iter<char>, char>; _Args =
{std::basic_format_arg<std::basic_format_context<std::__format::_Sink_iter<char>,
char> >::handle}; _Element_t =
std::__format::_Arg_store<std::basic_format_context<std::__format::_Sink_iter<char>,
char>,
std::basic_format_arg<std::basic_format_context<std::__format::_Sink_iter<char>,
char> >::handle>::_Element_t]'
 3743 |           basic_format_arg<_Context> __arg(__v);
      |                                      ^~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3754:23:   required from
'std::__format::_Arg_store<_Context, _Args>::_Arg_store(_Tp& ...) [with _Tp =
{std::thread::id}; _Context =
std::basic_format_context<std::__format::_Sink_iter<char>, char>; _Args =
{std::basic_format_arg<std::basic_format_context<std::__format::_Sink_iter<char>,
char> >::handle}]'
 3754 |         : _M_args{_S_make_elt(__a)...}
      |                   ~~~~~~~~~~~^~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:3804:14:   required from 'auto
std::make_format_args(_Args& ...) [with _Context =
basic_format_context<__format::_Sink_iter<char>, char>; _Args = {thread::id}]'
 3804 |       return _Store(__fmt_args...);
      |              ^~~~~~~~~~~~~~~~~~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/format:4291:61:   required from
'std::string std::format(format_string<_Args ...>, _Args&& ...) [with _Args =
{thread::id}; string = __cxx11::basic_string<char>; format_string<_Args ...> =
basic_format_string<char, thread::id>]'
 4291 |     { return std::vformat(__fmt.get(),
std::make_format_args(__args...)); }
      |                                        ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~
prog.cc:8:29:   required from here
    8 |     std::cout << std::format("{}", std::this_thread::get_id()) <<
std::endl;
      |                  ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/opt/wandbox/gcc-head/include/c++/15.0.0/thread:334:44: error:
'std::__cxx11::basic_ostringstream<char> __os' has incomplete type
  334 |           std::basic_ostringstream<_CharT> __os;
      |                                            ^~~~


It seems missing include <sstream> at <thread>.

[Bug libstdc++/115099] compilation error: format thread::id

[de34 at live dot cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099

Jiang An <de34 at live dot cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |de34 at live dot cn

--- Comment #1 from Jiang An <de34 at live dot cn> ---
I guess we shouldn't include <sstream> in <thread>. There should be far more
simple ways to obtain thread::id's text representation.

[Bug libstdc++/115099] compilation error: format thread::id

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-05-17
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org
   Target Milestone|---                         |14.2
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED

[Bug libstdc++/115099] compilation error: format thread::id

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099

--- Comment #2 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:1a5e4dd83788ea4c049d354d83ad58a6a3d747e6

commit r15-770-g1a5e4dd83788ea4c049d354d83ad58a6a3d747e6
Author: Jonathan Wakely <jwakely@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.

[Bug libstdc++/115099] compilation error: format thread::id

[cvs-commit at gcc dot gnu.org]

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
<redi@gcc.gnu.org>:

https://gcc.gnu.org/g:4896bb3199253dc350f8fb5ff63370310ca27ce2

commit r14-10232-g4896bb3199253dc350f8fb5ff63370310ca27ce2
Author: Jonathan Wakely <jwakely@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)

[Bug libstdc++/115099] compilation error: format thread::id

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115099

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Fixed for 14.2, thanks for the report.