Fix MSVC workaround with FMT_ENFORCE_COMPILE_STRING

[yeswalrus]

Per comments in #2038, This is just the proper fix for a previous attempt at working around this compile error. Though Microsoft reported that a related error had been resolved (https://developercommunity.visualstudio.com/content/problem/1256077/internal-compiler-failure-with-macro-defining-lamb.html) in the latest build of MSVC, the more complex case is still a problem, which I've reported here: https://developercommunity.visualstudio.com/content/problem/1277597/internal-compiler-c0001-error-on-complex-nested-la.html

[vitaut]

Could you post a full repro and the error from MSVC for future reference?

[yeswalrus]

Full Repro can be achieved by simply disabling this #ifdef. I suspect the error has something to do with the depth of template nesting but wasn't able to narrow down the repro case any further. Full log of what I see locally here:

>------ Build All started: Project: fmt, Configuration: x64-Debug (default) ------
  [1/5] Linking CXX executable bin\posix-mock-test.exe
  [2/5] Building CXX object test\CMakeFiles\enforce-compiletime-test.dir\enforce-compiletime-test.cc.obj
  FAILED: test/CMakeFiles/enforce-compiletime-test.dir/enforce-compiletime-test.cc.obj 
  C:\PROGRA~2\MICROS~1\2019\COMMUN~1\VC\Tools\MSVC\1428~1.293\bin\Hostx64\x64\cl.exe  /nologo /TP -DFMT_ENFORCE_COMPILE_STRING -DFMT_LOCALE -DGTEST_HAS_STD_WSTRING=1 -DGTEST_LANG_CXX11=0 -D_SILENCE_TR1_NAMESPACE_DEPRECATION_WARNING=1 -D_VARIADIC_MAX=10 -I..\..\..\include -I..\..\..\test\gtest -I..\..\..\test\gmock -I..\..\..\test\. /DWIN32 /D_WINDOWS /GR /EHsc /Zi /Ob0 /Od /RTC1 -MDd /showIncludes /Fotest\CMakeFiles\enforce-compiletime-test.dir\enforce-compiletime-test.cc.obj /Fdtest\CMakeFiles\enforce-compiletime-test.dir\ /FS -c ..\..\..\test\enforce-compiletime-test.cc
C:\dev\yeswalrus\fmt\include\fmt\format.h(3279): fatal error C1001: Internal compiler error.
  (compiler file 'D:\a01\_work\6\s\src\vctools\Compiler\CxxFE\sl\p1\c\symbols.c', line 31449)
   To work around this problem, try simplifying or changing the program near the locations listed above.
  If possible please provide a repro here: https://developercommunity.visualstudio.com 
  Please choose the Technical Support command on the Visual C++ 
   Help menu, or open the Technical Support help file for more information
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1602): note: see reference to function template instantiation 'void fmt::v7::detail::check_format_string<Rep&,S,0>(S)' being compiled
          with
          [
              Rep=__int64,
              S=fmt::v7::detail::format_duration_value::<lambda_0fb45198f1f1e3f7491065cca1733391>::()::FMT_COMPILE_STRING
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1808): note: see reference to function template instantiation 'fmt::v7::format_arg_store<fmt::v7::basic_format_context<fmt::v7::detail::buffer_appender<wchar_t>,wchar_t>,intmax_t> fmt::v7::make_args_checked<Rep&,S,wchar_t>(const S &,const __int64 &)' being compiled
          with
          [
              Rep=__int64,
              S=fmt::v7::detail::format_duration_value::<lambda_0fb45198f1f1e3f7491065cca1733391>::()::FMT_COMPILE_STRING
          ]
  C:\dev\yeswalrus\fmt\include\fmt/chrono.h(778): note: see reference to function template instantiation 'std::back_insert_iterator<fmt::v7::basic_memory_buffer<wchar_t,500,std::allocator<wchar_t>>> fmt::v7::format_to<OutputIt,fmt::v7::detail::format_duration_value::<lambda_0fb45198f1f1e3f7491065cca1733391>::()::FMT_COMPILE_STRING,Rep&,true>(OutputIt,const S &,Rep &)' being compiled
          with
          [
              OutputIt=std::back_insert_iterator<fmt::v7::basic_memory_buffer<wchar_t,500,std::allocator<wchar_t>>>,
              Rep=__int64,
              S=fmt::v7::detail::format_duration_value::<lambda_0fb45198f1f1e3f7491065cca1733391>::()::FMT_COMPILE_STRING
          ]
  C:\dev\yeswalrus\fmt\include\fmt/chrono.h(1158): note: see reference to function template instantiation 'OutputIt fmt::v7::detail::format_duration_value<Char,_Rep,std::back_insert_iterator<fmt::v7::basic_memory_buffer<wchar_t,500,std::allocator<wchar_t>>>,0>(OutputIt,Rep,int)' being compiled
          with
          [
              OutputIt=std::back_insert_iterator<fmt::v7::basic_memory_buffer<wchar_t,500,std::allocator<wchar_t>>>,
              Char=wchar_t,
              _Rep=__int64,
              Rep=__int64
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1119): note: see reference to function template instantiation 'fmt::v7::detail::buffer_appender<wchar_t> fmt::v7::formatter<Arg,wchar_t,void>::format<Context>(const std::chrono::duration<__int64,std::ratio<1,1>> &,FormatContext &)' being compiled
          with
          [
              Arg=std::chrono::duration<__int64,std::ratio<1,1>>,
              Context=fmt::v7::wformat_context,
              FormatContext=fmt::v7::wformat_context
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1119): note: see reference to function template instantiation 'fmt::v7::detail::buffer_appender<wchar_t> fmt::v7::formatter<Arg,wchar_t,void>::format<Context>(const std::chrono::duration<__int64,std::ratio<1,1>> &,FormatContext &)' being compiled
          with
          [
              Arg=std::chrono::duration<__int64,std::ratio<1,1>>,
              Context=fmt::v7::wformat_context,
              FormatContext=fmt::v7::wformat_context
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1108): note: see reference to function template instantiation 'void fmt::v7::detail::value<Context>::format_custom_arg<T,fmt::v7::formatter<T,wchar_t,void>>(const void *,fmt::v7::basic_format_parse_context<wchar_t,fmt::v7::detail::error_handler> &,Context &)' being compiled
          with
          [
              Context=fmt::v7::wformat_context,
              T=std::chrono::duration<__int64,std::ratio<1,1>>
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1105): note: see reference to function template instantiation 'void fmt::v7::detail::value<Context>::format_custom_arg<T,fmt::v7::formatter<T,wchar_t,void>>(const void *,fmt::v7::basic_format_parse_context<wchar_t,fmt::v7::detail::error_handler> &,Context &)' being compiled
          with
          [
              Context=fmt::v7::wformat_context,
              T=std::chrono::duration<__int64,std::ratio<1,1>>
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1456): note: see reference to function template instantiation 'fmt::v7::detail::value<Context>::value<U>(const T &)' being compiled
          with
          [
              Context=fmt::v7::wformat_context,
              U=std::chrono::duration<__int64,std::ratio<1,1>>,
              T=std::chrono::duration<__int64,std::ratio<1,1>>
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1456): note: see reference to function template instantiation 'fmt::v7::detail::value<Context>::value<U>(const T &)' being compiled
          with
          [
              Context=fmt::v7::wformat_context,
              U=std::chrono::duration<__int64,std::ratio<1,1>>,
              T=std::chrono::duration<__int64,std::ratio<1,1>>
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1566): note: see reference to function template instantiation 'fmt::v7::detail::value<Context> fmt::v7::detail::make_arg<true,Context,fmt::v7::detail::type::custom_type,std::chrono::duration<__int64,std::ratio<1,1>>,0>(const T &)' being compiled
          with
          [
              Context=fmt::v7::wformat_context,
              T=std::chrono::duration<__int64,std::ratio<1,1>>
          ]
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1559): note: while compiling class template member function 'fmt::v7::format_arg_store<fmt::v7::basic_format_context<fmt::v7::detail::buffer_appender<wchar_t>,wchar_t>,std::chrono::duration<__int64,std::ratio<1,1>>>::format_arg_store(const std::chrono::duration<__int64,std::ratio<1,1>> &)'
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1603): note: see reference to function template instantiation 'fmt::v7::format_arg_store<fmt::v7::basic_format_context<fmt::v7::detail::buffer_appender<wchar_t>,wchar_t>,std::chrono::duration<__int64,std::ratio<1,1>>>::format_arg_store(const std::chrono::duration<__int64,std::ratio<1,1>> &)' being compiled
  C:\dev\yeswalrus\fmt\include\fmt\core.h(1881): note: see reference to class template instantiation 'fmt::v7::format_arg_store<fmt::v7::basic_format_context<fmt::v7::detail::buffer_appender<wchar_t>,wchar_t>,std::chrono::duration<__int64,std::ratio<1,1>>>' being compiled
  ..\..\..\test\enforce-compiletime-test.cc(26): note: see reference to function template instantiation 'std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>> fmt::v7::format<ChronoTest_FormatWide_Test::TestBody::<lambda_6ba65e1b6bab98328b07f2c69485565d>::()::FMT_COMPILE_STRING,std::chrono::seconds,wchar_t,0>(const S &,std::chrono::seconds &&)' being compiled
          with
          [
              S=ChronoTest_FormatWide_Test::TestBody::<lambda_6ba65e1b6bab98328b07f2c69485565d>::()::FMT_COMPILE_STRING
          ]
  [3/5] Building CXX object test\CMakeFiles\chrono-test.dir\chrono-test.cc.obj
  FAILED: test/CMakeFiles/chrono-test.dir/chrono-test.cc.obj 

[vitaut]

Considering that MSVC 2017 is too buggy to support FMT_STRING I don't think it makes sense to enable FMT_ENFORCE_COMPILE_STRING on this compiler. Therefore the workaround is not needed.

[yeswalrus]

This is happening in the latest MSVC, 2019. This is also the only place it fails.

[vitaut]

This is happening in the latest MSVC, 2019.

That's unfortunate but I don't think the version matters. If MSVC fails in such basic case, it can fail on user code making enabling FMT_ENFORCE_COMPILE_STRING problematic for this compiler.