GNU project C and C++ compiler

-pthread
    Adds support for multithreading with the pthreads library.  This option sets flags for both the
    preprocessor and linker.

Darwin Options

These options are defined for all architectures running the Darwin operating system.  They are useful for
compatibility with other Mac OS compilers.

-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 you specify -o when compiling more than one input file, or you are producing an executable file as
    output, all the source files on the command line will be compiled at once.

    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, and all preprocessed C source on standard
    output.