Fix build error on code page 949

[raeperd]

When I built without making any changes to this project, I found the following error.

[main] Building folder: cpp_starter_project 
[build] Starting build
[proc] Executing command: "C:\Program Files\CMake\bin\cmake.EXE" --build c:/lab/cpp_starter_project/build --config Debug --target ALL_BUILD -- /maxcpucount:14
[build] Microsoft (R) Build Engine version 16.5.0+d4cbfca49 for .NET Framework
[build] Copyright (C) Microsoft Corporation. All rights reserved.
[build] 
[build]   Checking Build System
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/src/CMakeLists.txt
[build]   catch_main.cpp
[build]   main.cpp
[build] C:\Users\PC\.conan\data\fmt\6.2.0\_\_\package\9ffec4a59d60a2ccf636e06ba57253e21417f01b\include\fmt/core.h(327,35): error C2220: the following warning is treated as an error [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build] C:\Users\PC\.conan\data\fmt\6.2.0\_\_\package\9ffec4a59d60a2ccf636e06ba57253e21417f01b\include\fmt/core.h(327,35): warning C4566: character represented by universal-character-name '\u00B5' cannot be represented in the current code page (949) [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build] C:\Users\PC\.conan\data\spdlog\1.5.0\_\_\package\cf72f4f3a71ff1fe5381d0f0ebe068c867c28045\include\spdlog/details/circular_q.h(1,1): warning C4819: The file contains a character that cannot be represented in the current code page (949). Save the file in Unicode format to prevent data loss [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build]   catch_main.vcxproj -> C:\lab\cpp_starter_project\build\lib\catch_main.lib
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   tests.cpp
[build]   constexpr_tests.cpp
[build]   constexpr_tests.cpp
[build]   constexpr_tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\constexpr_tests.exe
[build]   tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\tests.exe
[build]   relaxed_constexpr_tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\relaxed_constexpr_tests.exe
[build] Build finished with exit code 1

And that only needs one line fix. add compile option for utf8

Unlike what I've been doing like this reference, I found author of this repo might not want to modify compile options. For that consistency, this request should not be merged.
Still, I wonder if someone else who has the same problem as me will help.

I think following cmake configure log will be enough to explain my environment

[main] Building folder: cpp_starter_project 
[build] Starting build
[proc] Executing command: "C:\Program Files\CMake\bin\cmake.EXE" --build c:/lab/cpp_starter_project/build --config Debug --target ALL_BUILD -- /maxcpucount:14
[build] Microsoft (R) Build Engine version 16.5.0+d4cbfca49 for .NET Framework
[build] Copyright (C) Microsoft Corporation. All rights reserved.
[build] 
[build]   Checking Build System
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/src/CMakeLists.txt
[build]   catch_main.cpp
[build]   main.cpp
[build] C:\Users\PC\.conan\data\fmt\6.2.0\_\_\package\9ffec4a59d60a2ccf636e06ba57253e21417f01b\include\fmt/core.h(327,35): error C2220: the following warning is treated as an error [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build] C:\Users\PC\.conan\data\fmt\6.2.0\_\_\package\9ffec4a59d60a2ccf636e06ba57253e21417f01b\include\fmt/core.h(327,35): warning C4566: character represented by universal-character-name '\u00B5' cannot be represented in the current code page (949) [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build] C:\Users\PC\.conan\data\spdlog\1.5.0\_\_\package\cf72f4f3a71ff1fe5381d0f0ebe068c867c28045\include\spdlog/details/circular_q.h(1,1): warning C4819: The file contains a character that cannot be represented in the current code page (949). Save the file in Unicode format to prevent data loss [C:\lab\cpp_starter_project\build\src\intro.vcxproj]
[build]   catch_main.vcxproj -> C:\lab\cpp_starter_project\build\lib\catch_main.lib
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   Building Custom Rule C:/lab/cpp_starter_project/test/CMakeLists.txt
[build]   tests.cpp
[build]   constexpr_tests.cpp
[build]   constexpr_tests.cpp
[build]   constexpr_tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\constexpr_tests.exe
[build]   tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\tests.exe
[build]   relaxed_constexpr_tests.vcxproj -> C:\lab\cpp_starter_project\build\bin\relaxed_constexpr_tests.exe
[build] Build finished with exit code 1

[ddalcino]

It looks like the fmt developers fixed this bug (see: fmtlib/fmt#1625) when they released version 7.0.0. If you look at their current source, they added a warning suppression, since they have determined that it’s a false positive: https://github.com/fmtlib/fmt/blob/61602a75db980737870e7f5e91de99e49dcd1c9e/include/fmt/core.h#L320

I may be wrong, but I think it makes more sense for this project to pull in a newer version of fmt rather than tell all of our MSVC users that they have to use UTF8.

Edit: Additionally, if you still want to add that compile option, you’ll need to put it behind a conditional that checks which compiler you’re using. Clang and gcc both report errors when given that option, or, at least they did on Travis CI.

[raeperd]

Thanks @ddalcino, for your kind explanation. I didn't check out fmt library for that update.
As u described, it is absolutely better to pull newer version of fmt library.
Because that would be different type of work from this pull request, I'm closing this request first, and work on another branch for that later.

While I'm working on this travis bug, found another bugs for this. So i will report this later on. Thanks.