redefinition of struct fmt_detail::time_zone when compile with fmt

[zhangzq]

Describe the bug

I used fmt in my project. But got redefinition of struct fmt_detail::time_zone error when compile my project.

I found the problem is quill/std/FilesystemPath.h. Everything are find when I not include this path.

To Reproduce

the example code (save in t.cpp):

#include "quill/Backend.h"
#include "quill/Frontend.h"
#include "quill/LogMacros.h"
#include "quill/Logger.h"
#include "quill/sinks/ConsoleSink.h"
#include <string_view>
#include "fmt/base.h"

#include "quill/std/Array.h"
#include "quill/std/Vector.h"
#include "quill/std/FilesystemPath.h"
#include "fmt/std.h"
#include "fmt/ranges.h"

int main()
{
  quill::Backend::start();

  quill::Logger* logger = quill::Frontend::create_or_get_logger(
    "root", quill::Frontend::create_or_get_sink<quill::ConsoleSink>("sink_id_1"));
                                                                                                                                                                                                                                                                                          fmt::print("{}", std::vector<int>{{1, 2, 3}});

  LOG_INFO(logger, "Hello from {}!", std::string_view{"Quill"});
}

when compile with (the quill/fmt headers installed in /opt/include, and quill/fmt library installed in /opt/lib):

g++ t.cpp -o t -I /opt/include -L /opt/lib -l quill -l fmt

result in following compile error:

In file included from /opt/include/fmt/ostream.h:23,
                 from /opt/include/fmt/std.h:12,
                 from t.cpp:13:
/opt/include/fmt/chrono.h:26:8: error: redefinition of ‘struct fmt_detail::time_zone’
   26 | struct time_zone {
      |        ^~~~~~~~~
In file included from /opt/include/quill/bundled/fmt/ostream.h:23,
                 from /opt/include/quill/bundled/fmt/std.h:12,
                 from /opt/include/quill/std/FilesystemPath.h:16,
                 from t.cpp:12:
/opt/include/quill/bundled/fmt/chrono.h:26:8: note: previous definition of ‘struct fmt_detail::time_zone’
   26 | struct time_zone {
      |        ^~~~~~~~~
/opt/include/fmt/chrono.h:33:38: error: redefinition of ‘template<class ... T> fmt_detail::time_zone* fmt_detail::current_zone(T ...)’
   33 | template <typename... T> inline auto current_zone(T...) -> time_zone* {
      |                                      ^~~~~~~~~~~~
/opt/include/quill/bundled/fmt/chrono.h:33:38: note: ‘template<class ... T> fmt_detail::time_zone* fmt_detail::current_zone(T ...)’ previously declared here
   33 | template <typename... T> inline auto current_zone(T...) -> time_zone* {
      |                                      ^~~~~~~~~~~~
/opt/include/fmt/chrono.h:37:38: error: redefinition of ‘template<class ... T> void fmt_detail::_tzset(T ...)’
   37 | template <typename... T> inline void _tzset(T...) {}
      |                                      ^~~~~~
/opt/include/quill/bundled/fmt/chrono.h:37:38: note: ‘template<class ... T> void fmt_detail::_tzset(T ...)’ previously declared here
   37 | template <typename... T> inline void _tzset(T...) {}
      |                                      ^~~~~~

Expected Behaviour

There should be no conflict.

Environment Details

using quill master (be6c292)，and fmt master (aabe6391), in ubuntu 24.04, with default gcc 13.3.0.

[odygrd]

thanks a lot for reporting this. This new namespace was introduced in the latest libfmt release and that is a bit unexpected. I will release a new version with a fix once libfmt 11.1.3 is available.

It has to be renamed to fmtquill_detail but the ideal solution would be if in libfmt the existing fmt::detail namespace is used

[odygrd]

fmtlib/fmt#4324