C++ code snippets

Finding the C++ standard from g++

Thanks to this SO answer, one can find the C++ standard version supported by your g++ binary (this is not the version of the compiler).

g++ -dM -E -x c++ /dev/null | grep -F __cplusplus

A hacky way to list all possible standard versions is to pass an invalid -std flag. For instance,

g++ -std=foobar -dM -E -x c++ /dev/null | grep -F __cplusplus

Pick your favorite.

error: invalid value 'foobar' in '-std=foobar'
note: use 'c++98' or 'c++03' for 'ISO C++ 1998 with amendments' standard
note: use 'gnu++98' or 'gnu++03' for 'ISO C++ 1998 with amendments and GNU extensions' standard
note: use 'c++11' for 'ISO C++ 2011 with amendments' standard
note: use 'gnu++11' for 'ISO C++ 2011 with amendments and GNU extensions' standard
note: use 'c++14' for 'ISO C++ 2014 with amendments' standard
note: use 'gnu++14' for 'ISO C++ 2014 with amendments and GNU extensions' standard
note: use 'c++17' for 'ISO C++ 2017 with amendments' standard
note: use 'gnu++17' for 'ISO C++ 2017 with amendments and GNU extensions' standard
note: use 'c++2a' for 'Working draft for ISO C++ 2020' standard
note: use 'gnu++2a' for 'Working draft for ISO C++ 2020 with GNU extensions' standard