.. _c++-comments: C++ Style Comments ****************** .. index:: // .. index:: C++ comments .. index:: comments, C++ style In GNU C, you may use C++ style comments, which start with :samp:`//` and continue until the end of the line. Many other C implementations allow such comments, and they are included in the 1999 C standard. However, C++ style comments are not recognized if you specify an :option:`-std` option specifying a version of ISO C before C99, or :option:`-ansi` (equivalent to :option:`-std=c90`).