GNU project C and C++ compiler

-mt
-pthread
    Add support for multithreading using the POSIX threads library.  This option sets flags for both the
    preprocessor and linker.  It does not affect the thread safety of object code produced by the
    compiler or that of libraries supplied with it.  These are HP-UX specific flags.

-o file
    Place output in file file.  This applies regardless to whatever sort of output is being produced,
    whether it be an executable file, an object file, an assembler file or preprocessed C code.

    If -o is not specified, the default is to put an executable file in a.out, the object file for
    source.suffix in source.o, its assembler file in source.s, a precompiled header file in
    source.suffix.gch, and all preprocessed C source on standard output.