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- Subject: Re: out of memory
- From: David Jones <drj@...>
- Date: Mon, 07 Oct 2002 12:34:50 +0000
In message <3D9EED95.E914E7EB@gmx.de>, Edgar Toernig writes:
> > I do not know what the ANSI C standard says about using
> > realloc(x,0).
> ANSI C99 about memory management functions in general:
> If the size of the space requested is
> zero, the behavior is implementation-defined: either a null
> pointer is returned, or the behavior is as if the size were
> some nonzero value, except that the returned pointer shall
> not be used to access an object.
> and about realloc itself [the part where free is mentioned]:
> If the realloc function returns a null pointer
> when size is zero and ptr is not a null pointer, the object
> it pointed to has been freed.
> So it seems one cannot depend on realloc(x,0) to free x and my
> libc is not buggy (puh *g*). Perfectly legal behaviour: truncate
> to some small size and return a valid and unique pointer.
*ugh*. The wording in the ISO C Standard has changed between the 1989
version and the 1999 version. The 1989 version simply stated:
"If size is zero and ptr is not a null pointer, the object it pointed to
has been freed." (or something essentially equivalent, I haven't got the
standard here in front of me). The 1999 version added the qualification
"If the realloc function returns a null pointer when ... ".
In other words, lua was fine under the old, 1989, version of the C
standard, but now opens itself to a hosing by new implementations of the
lua should change.