Re: Can I Trust Pointer Arithmetic In Re-Allocated Memory?

On Sun, 13 Aug 2006 16:14:19 UTC, "Bill Reid"
<hormelfree@xxxxxxxxxxxxxxxx> wrote:

What I forgot was that if I don't malloc() the block first, if I
realloc() in a loop I get a memory access exception. I hate it
when that happens...

void *p = NULL; /* we have no memory yet */
void *temp; /* realloc will set it */

size_t size = 0; /* we calculate the size in the loop before we call
realloc */
....
for (....) {
....
if ((temp = realloc(p, size) != NULL) {
/* realloc failed */
return NULL; /* or some other error code */
}
p = temp;
....
}
free(p);

will work always - except your implementation is really broken. But
hten trow your compiler into trash and get another one.

Maybe it IS a bug in the compiler, if it wasn't so easy to work
around, I might actually worry about it more. As it is, I did a
search on the compiler maker's web-site for any information
on known bugs, came up with nothing, and left a question on
the discussion forum about it, see if anybody knows anything...

I would say you have forgotten to initialise the pointer given to
realloc with NULL signalling it that thre is currently nothing to
realloc but malloc.

--
Tschau/Bye
Herbert

Visit http://www.ecomstation.de the home of german eComStation
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