I have a piece of code that looks like the following. Let\'s say it\'s in a file named example.cpp
#include
#include
I believe that it is possible to tell by looking at the man page (at least for g++):
Under the description of -std, the man page lists all C++ standards, including the GNU dialects. Under one specific standard, it is rather inconspicuously stated, This is the default for C++ code. (there is an analogous statement for C standards: This is the default for C code.).
For instance, for g++/gcc version 5.4.0, this is listed under gnu++98/gnu++03, whereas for g++/gcc version 6.4.0, this is listed under gnu++14.