strlen(null) is pretty straightforward, although being a pure function the compiler might rearrange things. if (!s) puts("hi"); strlen(s); I don't thi

strlen(null) is pretty straightforward, although being a pure function the compiler might rearrange things. if (!s) puts("hi"); strlen(s); I don't think that's guaranteed to print hi if s is null. More fun is memset(0,0,0) which is technically verboten.