STINNER Victor firstname.lastname@example.org added the comment:
The -x command line option is now stored as PyConfig.skip_source_first_line, documented as: "Skip the first line of the source?" https://docs.python.org/dev/c-api/init_config.html#c.PyConfig.skip_source_fi...
Include/cpython/initconfig.h contains a longer comment:
/* Skip the first line of the source ('run_filename' parameter), allowing use of non-Unix forms of "#!cmd". This is intended for a DOS specific hack only.
Set by the -x command line option. */ int skip_source_first_line;