On 11/11/18 5:38 PM, Jakub Wilk wrote: > * Jonny Grant <jg@xxxxxxxx>, 2018-11-11, 14:26: >> BTW, C Spec says NULL is a pointer that doesn't have a type, > > Not quite. NULL is a “null pointer constant”, which could be an integer, > not necessarily a pointer. > > That said, the POSIX.1-2008 standard guarantees it's a pointer. (AFAICT, > the earlier standards did not guarantee this.) > > On the other hand, NULL is not defined as a pointer in C++. And also perhaps not in C? At least not historically; I'm not sure if that's still true. >> there is no need to cast it to (char *) -- should that be taken out? > > The execl*() functions are variadic, which makes them picky about > argument types. Theses casts are certainly needed when NULL is not > defined as a pointer. Exactly. > It's less clear to me if they are still necessary when NULL is defined > as (void*)0. No, I believe they're not. > Either way, I recommend keeping the cast for the sake of portability. Exactly. You don't know how a particular implementation has defined NULL. Could be `(void *) 0'. Or it could be just `0'. Thanks, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/
