I do write C code on a daily basis since 2001 and I don't know why I always believed that free(NULL) would crash, so I always used the painful construction:
if (p)
free(p);
Until yesterday! While talking to Lennart Poettering and we bet about that. Damn, I was so sure about it, but I'd really want to believe I was wrong, since I could avoid such stupid "if". Well, after we got David Zeuthen's phone we checked the free(3) man page and I was proved wrong!
Thanks Lennart, I owe you some bucks ;-)