Compile error when using spdlog with FMT_ENFORCE_COMPILE_STRING

[john4744]

I'm building an exe that uses spdlog and fmt. I'm building with FMT_ENFORCE_COMPILE_STRING defined. This is causing the following compile error:

c:\apps\3rdparty\spdlog\include\spdlog\fmt\bundled\core.h(603,39): error C2338: FMT_ENFORCE_COMPILE_STRING requires all format strings to use FMT_STRING.
c:\apps\3rdparty\spdlog\include\spdlog\fmt\bundled\core.h(3057): message : see reference to function template instantiation 'void fmt::v8::detail::check_format_string<,char[21],0>(const S (&))' being compiled
        with
        [
            S=char [21]
        ]
c:\apps\3rdparty\spdlog\include\spdlog\fmt\bundled\format-inl.h(96): message : see reference to function template instantiation 'fmt::v8::basic_format_string<char>::basic_format_string<char[21],0>(const S (&))' being compiled
        with
        [
            S=char [21]
        ]
c:\apps\3rdparty\spdlog\include\spdlog\fmt\bundled\format-inl.h(96): message : see reference to function template instantiation 'fmt::v8::basic_format_string<char>::basic_format_string<char[21],0>(const S (&))' being compiled
        with
        [
            S=char [21]
        ]

Not sure what I'm doing wrong, any help would be appreciated. Thanks!

[tt4g]

Please wrap the format string with the FMT_STRING macro if define FMT_ENFORCE_COMPILE_STRING macro (this is fmt library feature.).

spdlog::info(FMT_STRING("Log with {}."), "macro"); // OK.

spdlog::info("Log without {}.", "macro"); // Assertion error.

[john4744]

Thanks for the feedback! In this case, I only have #include "spdlog/spdlog.h", no actual calls into the spdlog API. I think I may have tracked down the problem to a misconfiguration on my part 🤦‍♂️ . I noticed that the example project has SPDLOG_COMPILED_LIB defined and my project didn't. Adding this define to my project seems to resolve the compile error.

[john4744]

Actually, there still may be a problem here building for Android... When I include android_sink.h I get this compile error:

../../3rdparty/fmt/include/fmt/core.h:603:3: error: static_assert failed due to requirement 'is_compile_string<char [6]>::value' "FMT_ENFORCE_COMPILE_STRING requires all format strings to use FMT_STRING."
  static_assert(is_compile_string<S>::value,
  ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~
../../3rdparty/fmt/include/fmt/core.h:3071:13: note: in instantiation of function template specialization 'fmt::v8::detail::check_format_string<int &, char [6], 0>' requested here
    detail::check_format_string<Args...>(s);
            ^
../../3rdparty/spdlog/include/spdlog/details/fmt_helper.h:110:54: note: in instantiation of function template specialization 'fmt::v8::basic_format_string<char, int &>::basic_format_string<char [6], 0>' requested here
        fmt_lib::format_to(std::back_inserter(dest), "{:02}", n);

I'm building with SPDLOG_COMPILED_LIB and FMT_ENFORCE_COMPILE_STRING defined.

[tt4g]

The FMT_STRING macro is missing here:

spdlog/include/spdlog/details/fmt_helper.h

Lines 101 to 112 in 0d8197c

	inline void pad2(int n, memory_buf_t &dest)
	{
	if (n >= 0 && n < 100) // 0-99
	{
	dest.push_back(static_cast<char>('0' + n / 10));
	dest.push_back(static_cast<char>('0' + n % 10));
	}
	else // unlikely, but just in case, let fmt deal with it
	{
	fmt_lib::format_to(std::back_inserter(dest), "{:02}", n);
	}
	}

The following fix should work around the problem.

-fmt_lib::format_to(std::back_inserter(dest), "{:02}", n); 
+fmt_lib::format_to(std::back_inserter(dest), FMT_STRING("{:02}"), n); 

And can you submit a PR?

[john4744]

I think I may have found a few other spots that need the FMT_STRING, I'll submit a PR.