C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
       .CPP, .c++, .cp, or .cxx; C++ header files often use .hh or .H; and
       preprocessed C++ files use the suffix .ii.  GCC recognizes files with
       these names and compiles them as C++ programs even if you call the com‐
       piler the same way as for compiling C programs (usually with the name
       gcc).

       However, the use of gcc does not add the C++ library.  g++ is a program
       that calls GCC and treats .c, .h and .i files as C++ source files
       instead of C source files unless -x is used, and automatically speci‐
       fies linking against the C++ library.  This program is also useful when
       precompiling a C header file with a .h extension for use in C++ compi‐
       lations.  On many systems, g++ is also installed with the name c++.

       When you compile C++ programs, you may specify many of the same com‐
       mand-line options that you use for compiling programs in any language;
       or command-line options meaningful for C and related languages; or
       options that are meaningful only for C++ programs.