D. Richard Hipp wrote:
On Wed, 2005-06-29 at 15:19 +0300, Lauri Nurmi wrote:
So, basically, is there a reason why sqlite3Malloc(n) & co should even
try to allocate zero bytes, instead of just returning NULL if n==0? Does
a pointer pointing to zero bytes of memory have any use anyway?
Yes. A NULL return from sqlite3Malloc() is an error condition meaning
that you have run out of memory. That is very different from returning
a zero-length memory allocation.
I see the difference, yes. Still, I'm not convinced that doing a
malloc(0) is a good thing.
I found this quotation from the net
<http://lists.freebsd.org/pipermail/freebsd-net/2004-February/002946.html>,
it is probably from the C99 standard:
---
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.
---
So malloc(0) may return NULL, and even if it doesn't, the pointer should
not be used.
You wouldn't want to substitute a NULL for an empty string in SQL would
you? Having sqlite3Malloc return NULL for a zero-length allocation is
roughly the same thing.
Hmm, an empty (C-style) string doesn't fit into zero bytes, it needs one
byte for the '\0'. If you have a pointer pointing to zero allocated
bytes, you can't even use strlen() or anything else on it [according to
the quotation above].
--
Lauri Nurmi
Ksenos DVR Development
