Christian Weisgerber <na...@mips.inka.de> wrote: > NULL is not magic. We #define NULL to 0. It is 0 that is automatically > treated as a null pointer _in pointer contexts_. If a function has > a variable number of arguments, like execlp() in this case, the > compiler can't know if you are passing 0 the integer or 0 the null > pointer. It defaults to the former, that's why the cast is needed.
A further note: On OpenBSD, the null pointer has a zero bit pattern, so the only difference between 0 and (void *)0 is that these are 32 and 64-bit values, respectively, on our LP64 platforms. In practice, our LP64 architectures pass the first handful of function arguments in registers. One argument in each 64-bit register, and if you load a 32-bit value into a register it is (sign-)extended to 64 bits. In most cases this will save your ass if you erroneously pass 0 in place of (void *)0 to a variable argument function. Do *not* rely on this. -- Christian "naddy" Weisgerber na...@mips.inka.de
