Has anyone ever seen any behaviour other than a segfault in the wild, though? Would any real-world compiler author decide that some other behaviour was reasonable? I can't imagine making that decision myself.
printf("a=%p *a=%d", a, *a);
if (a == NULL) return;
unsigned short *a = 0;
((void (*)(void))a)();
On R8C with the NC30 compiler there are no warnings and the output is:
MOV.W:Q #0H, -2H[FB]
MOV.W:G -2H[FB], R0
MOV.W:Q #0H, R2
JSRI.A R2R0
(I think I read about this somewhere, but it was a while ago, and I never really programmed for DOS (well, one little program to set the serial port to some specific settings, but that was about ten lines including whitespace and a little comment explaining what the code did).)