void *realloc(void *ptr, size-t size);
C90: "[…] If the space cannot be allocated, the object pointed to by ptr
is unchanged. If size is zero and ptr is not a null pointer, the object
it points to is freed."
C99TC2 (also C99TC3 and C11): "[…] If memory for the new object cannot
be allocated, the old object is not deallocated and its value is unchanged."
C17: "If size is zero and memory for the new object is not allocated, it
is implementation-defined whether the old object is deallocated. If the
old object is not deallocated, its value shall be unchanged."
C23 (same in current C2Y draft): "[…] if the size is zero, the behavior
is undefined. If memory for the new object is not allocated, the old
object is not deallocated and its value is unchanged."
Currently, our malloc and realloc cannot allocate an object of size
zero, they return NULL on such a request, and realloc does free. To me
that looks compliant with C90, C17 and C23, but not C99.
I would like to change that to allowing allocation of zero-sized objects
instead. Then, malloc(0) and realloc(ptr, 0) would return a non-null
pointer. This would be compliant with C99, C17 and C23, but not C90.
From my side, this change is not motivated by a preference for the new
semantics, but by it being the simplest to implement, thus reducing code
size for malloc and realloc a bit.
Philipp
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