I am currently working on a setuid programme. My configure script passes '-o/dev/null' to compilers when it tests for features. Once I ran my configure script for TinyCC as root -- and it replaced /dev/null with a binary.

The behaviour is easy enough to reproduce:

$ tcc -v
tcc version 0.9.27 (x86_64 Linux)
$ ls -l /dev/null
crw-rw-rw- 1 root root 1, 3 Jul 26 17:46 /dev/null
$ cat <<eof >foo.c
int main(void) { return 0; }
eof
$ sudo tcc -o/dev/null foo.c
$ ls -l /dev/null
-rwxr-xr-x 1 root root 3128 Jul 26 17:49 /dev/null

Sure, in a way, that's technically correct, but still I think it'd be good if that were changed ;-).