Ages ago I worked with a system where malloc(0) incremented a counter and returned -1.
free(-1) decremented the counter.
This way you could check for leaks :p
replies(3):
free(-1) decremented the counter.
This way you could check for leaks :p
On most platforms an implementation could just return adjacent addresses from the top half of the address space. On 32-bit platforms it doesn't take long to run out of such address space however, and you don't want to waste the space for a bitmap allocator. I suppose you could just use a counter for each 64K region or something, so you can reuse it if the right number of elements has been freed ...
I know I've seen that somewhere, but may I ask what standard you're referring to?
> Each [...] allocation shall yield a pointer to an object disjoint from any other object. The pointer returned points to the start (lowest byte address) of the allocated space. If the space cannot be allocated, a null pointer shall be returned. If the size of the space requested is 0, the behavior is implementation-defined: either a null pointer shall be returned, or the behavior shall be as if the size were some non-zero value, except that the behavior is undefined if the returned pointer is used to access an object.
https://pubs.opengroup.org/onlinepubs/9799919799/functions/m...