On Sun, 6 Dec 2009, Markus Armbruster wrote: > malc <av1...@comtv.ru> writes: >
[..snip..] > > read(fd, malloc(0), 0) is just fine, because read() doesn't touch the > buffer when the size is zero. > [..snip..] Yet under linux the address is checked even for zero case. > > > > I don't know what a "valid pointer" in this context represents. > > I can talk standardese, if you prefer :) > > malloc() either returns either a null pointer or a pointer to the > allocated space. In either case, you must not dereference the pointer. > > OpenBSD chooses to return a pointer to the allocated space. It chooses > to catch common ways to dereference the pointer. > > Your "p = (void *)-1" is neither a null pointer nor can it point to > allocated space on your particular system. Hence, it cannot be a value > of malloc() for any argument, and therefore what read() does with it on > that particular system doesn't matter. > Here, i believe, you are inventing artificial restrictions on how malloc behaves, i don't see anything that prevents the implementor from setting aside a range of addresses with 31st bit set as an indicator of "zero" allocations, and then happily giving it to the user of malloc and consumming it in free. -- mailto:av1...@comtv.ru
