Hehe I went in fully expecting GNU to have managed making something as simple as echo.c relatively complex and with inconceivable options. Was not disappointed. They probably even managed to include a GNUism or two.
/* System V machines already have a /bin/sh with a v9 behavior.
Use the identical behavior for these machines so that the
existing system shell scripts won't barf. */
I mean... in main() there's a labeled goto for "just_echo" - even that section alone has something like 6 or 7 indentation levels. If I was writing satire code of GNU style I'd probably wouldn't have gone so far. Hehehe.
POSIX sed supports exactly 3 options (-n, -e and -f), the latest FreeBSD sed supports 10 (adding -E, -a, -I, -i, -l, -r and -u — the last two being GNUism compatibility options not necessarily available on older versions, they are not on my OSX machine) and GNU sed supports 9 short and an additional 4 long options. And that's not counting the extensions to the sed command set.
Definitely less convenient, but would make building cross-platform scripts much easier.