-P Inhibit generation of linemarkers in the output from the preprocessor. This might be useful when
running the preprocessor on something that is not C code, and will be sent to a program which might
be confused by the linemarkers.
Enable generation of linemarkers in the preprocessor output that will let the compiler know the
current working directory at the time of preprocessing. When this option is enabled, the
preprocessor will emit, after the initial linemarker, a second linemarker with the current working
directory followed by two slashes. GCC will use this directory, when it's present in the
preprocessed input, as the directory emitted as the current working directory in some debugging
information formats. This option is implicitly enabled if debugging information is enabled, but this
can be inhibited with the negated form -fno-working-directory. If the -P flag is present in the
command line, this option has no effect, since no "#line" directives are emitted whatsoever.