I am using the GNU Mingw 5.3.0 g++.exe for my compiler. I am trying to make my c++ library as reliable as possible by trying to compile it with the most strictest command line flags possible. So, what would those command line flags?
Off the top of my head, -std=c++14 -Wall -Wextra -pedantic, but there may be others. But, the only way to true way to test portability is to actually compile your code with multiple compilers on multiple platforms.