Use 'SPDLOG_FMT_RUNTIME' to fix compilation error throwed MSVC and fmt 9.1.x

[YunchengLiu]

This is the first time I submit a PR to the open source community. I try to submit code and instructions according to the rules I have learned, but there may be inappropriate places to do it. Please also point out my problems actively, I will try to do it as soon as possible. Learn and correct.

fmt 9.1.x added compile-time checks for wide strings, so when compiled with MSVC and this or later version of fmt(9.1.x), codes belows will throw a compilation error #(#2512).

spdlog/include/spdlog/sinks/daily_file_sink.h

Lines 80 to 84 in d011332

	# if defined(_MSC_VER) && defined(SPDLOG_WCHAR_FILENAMES) // for some reason msvc doesn't allow fmt::runtime(..) with wchar here
	return fmt::format(fmt_filename, now_tm);
	# else
	return fmt::format(SPDLOG_FMT_RUNTIME(fmt_filename), now_tm);
	# endif

When compiled with SPDLOG_WCHAR_FILENAMES with a newer verision of fmt(9.1.x) using MSVC, SPDLOG_FMT_RUNTIME will solve the problem.

#    if defined(_MSC_VER) && defined(SPDLOG_WCHAR_FILENAMES) // for some reason msvc doesn't allow fmt::runtime(..) with wchar here
#       if FMT_VERSION >= 90101
            // fmt 9.1.x added compile-time checks for wide strings
            // so when compiled with MSVC and this or later version of fmt
            // here should use 'SPDLOG_FMT_RUNTIME' to enable 'fmt::runtime(...)' for wchar to avoid compile error
            return fmt::format(SPDLOG_FMT_RUNTIME(fmt_filename), now_tm);
#       else
            return fmt::format(fmt_filename, now_tm);
#       endif
#    else
        return fmt::format(SPDLOG_FMT_RUNTIME(fmt_filename), now_tm);
#    endif

[gabime]

Thanks. Seems this all can be reduced to

// msvc doesn't allow fmt::runtime(..) with wchar, with fmtlib versions < 9.1.0
#if defined(SPDLOG_WCHAR_FILENAMES) && defined(_MSC_VER) && FMT_VERSION < 90101
   return fmt::format(fmt_filename, now_tm);
#else 
  return fmt::format(SPDLOG_FMT_RUNTIME(fmt_filename), now_tm);
#endif

[YunchengLiu]

Thanks. I have simplified the implement code.

[YunchengLiu]

@gabime Hi, I found the ci test failed at the code below.

spdlog/tests/test_eventlog.cpp

Line 44 in 77429b2

REQUIRE(record->NumStrings == 1);

It seems that this is not due to my PR, probably.

I want to know what should I do next, thanks.

[gabime]

Thanks @YunchengLiu . Merged.