And probably -Werror (all warnings become errors, breaking compilation).

Fun post. Now I know why everyone was raving about the clang error-messages:

    echo "void main() {}" > main.c


    gcc -Wall -Werror --std=c99 main.c 
    main.c:1:6: error: return type of ‘main’ is not ‘int’ [-Werror=main]
    cc1: all warnings being treated as errors


    clang -Wall -Werror --std=c99 main.c 
    main.c:1:1: error: 'main' must return 'int'
    void main() {}
    ^
    1 error generated.

    (not showing clangs pretty colours)

Nice suggestion. Although I can't seem where one would have to look for those "pretty colours" you mentioned, I certainly can't see any of them on my Mac terminal...

Can't help you there -- but I don't think I've set any exotic terminal variables or anything like that, and I get this:

http://i.imgur.com/BjWj7h6.png

FWIW, I have:

    COLORTERM=gnome-terminal
    TERM=screen

and Debian takes care of my termcap etc, afaik.

Think its his TERM env most likely being straight xterm (no color ansi escapes in the termcap iirc).

http://i.imgur.com/0Hzze9G.png

Thats me on osx running tmux with TERM=xterm-256color.

instead of -ansi, i'd argue that -std=c99 (or -std=c11) would be more appropriate. also note the -pedantic flag.

"-Weverything" if the code is compiling perfectly, but you're just bored. If you're not a complete masochist try turning off some of the sillier ones (-Wno-padded -Wno-unused-parameter -Wno-conversion)