Switch to C++17?

[FlorianSchwendinger]

I would suggest to switch to C++17 since C++11 was released a long time ago and HiGHS already uses C++17 features here.

In HiGHS/app/cxxopts.hpp

#define CXXOPTS_FALLTHROUGH
#ifdef __has_cpp_attribute
  #if __has_cpp_attribute(fallthrough)
    #undef CXXOPTS_FALLTHROUGH
    #define CXXOPTS_FALLTHROUGH [[fallthrough]]
  #endif
#endif

fallthrough is used which seams to be available since C++17.

[jajhall]

What's your view @galabovaa ?

[galabovaa]

Not sure, it's only the runtime options which are not included in the library. Seems a bit silly to upgrade just for this.

Thank you @FlorianSchwendinger, I did not notice cxxopts have increased the C++ version when I updated our version of cxxopts with their latest one. I'm a bit worried we may break highs for users who are still using C++11 or 14.

Perhaps it is time I add the "library only" build option, so we can require c++11 if only the library is being built? But that doesn't sounds great either. We could just downgrade cxxopts back to when they used c++11 only, or find another command line parsing tool?

[jajhall]

I agree with @galabovaa

[FlorianSchwendinger]

Build option

What I am doing now to aviod the

HiGHS/app/cxxopts.hpp:2303:5: warning: use of the 'fallthrough' attribute is a C++17 extension [-Wc++17-attribute-extensions]

message from CRAN is echo "" > HiGHS/app/CMakeLists.txt in my build script. So at least for me a option CMAKE file would be preferable. But what I am doing now should also work and is quite easy so there is no strong need for a option.

C++11 vs C++14 vs C++17

Some good news, the last version I submitted to CRAN I used already set(CMAKE_CXX_STANDARD 17) and it seamed to work (and is tested there at many platforms). But of course it could still break it for some users.