C++17: sym link to latest log

[xgdgsc]

I find it handy that glog creates symlink to latest log file. This patch requires c++17. So it may not be ok to merge but I think it might help people needing this feature searching in PRs.

[KjellKod]

Interesting!

It’s about time to lift G3log up to C++17 support so I can take a look at this in light of that coming work. I would have to make a last C++14 release and branch first (similar to what I did for C++11).

Have you looked at g3sinks repo?

I’m surprised you got it to compile though with C++17. I thought that the handling of result_of (deprecated) would cause some issues. Ref: https://en.cppreference.com/w/cpp/types/result_of

[KjellKod]

Lol. It’s early morning here. Of course you have looked at g3sinks ;)
Ha ha ha. So much for good writing (on my part) when you just wake up

[xgdgsc]

I just modified the cmake set (CMAKE_CXX_STANDARD 17) and it worked.

[KjellKod]

Please don't close this PR. I will get to it but it'll take a bit of time.

[KjellKod]

@xgdgsc sorry for the late action on this. Can you update the PR now that g3log is c++17 compatible? There are no reasons for the ifdef anymore

[KjellKod]

dang, apparently c++-17 still has the experimental/filesystem on gcc (Linux/OSX). I think that's why it's failing.

https://stackoverflow.com/questions/45867379/why-does-gcc-not-seem-to-have-the-filesystem-standard-library

[lederernc]

We use this snippet of code to make getting to std::filesystem work on a variety of compilers/platforms. Not exhaustive, of course.

Suggested change

	#include <filesystem>
	#if defined(_WIN32)
	# if _MSC_VER >= 1914
	# include <filesystem>
	namespace fs = std::filesystem;
	# else
	# include <experimental/filesystem>
	namespace fs = std::experimental::filesystem;
	# endif
	#elif defined(__GNUC__) && __GNUC__ <= 7
	# include <experimental/filesystem>
	namespace fs = std::experimental::filesystem;
	#elif defined(__GNUC__) && __GNUC__ >= 8
	# include <filesystem>
	namespace fs = std::filesystem;
	#elif defined(__clang__) && __clang_major__ <= 8
	# include <experimental/filesystem>
	namespace fs = std::experimental::filesystem;
	#elif defined(__clang__) && __clang_major__ <= 10
	# include <filesystem>
	namespace fs = std::filesystem;
	#endif

[KjellKod]

I wonder if this could be used?
Not sure on Windows but I think it works on Linux and OSX

// since C++ 20
#include <version>

#ifdef __cpp_lib_filesystem
    #include <filesystem>
    using fs = std::filesystem;
#elif __cpp_lib_experimental_filesystem
    #include <experimental/filesystem>
    using fs = std::experimental::filesystem;
#else
    #error "no filesystem support ='("
#endif

[xgdgsc]

Or use https://github.com/gulrak/filesystem?

[lederernc]

I think having just made the effort get onto c++17 it makes more sense to start using it.

[KjellKod]

Tried it out here: #439
Windows doesn't seem to have good support for std::filesystem yet