Re: realloc

Re: realloc

[Mehran Rezaei]

Chuck Winters wrote:

> Hello all,
>         Anyone know why a program would freeze at realloc?  I thought
> if there was a problem, realloc would just fail.
>
> Thanks,
> Chuck
> -
> To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Hi,

The problem happens just because of specific allocator that you are using. You can
avoid it by simply malloc new area, copy the content and free previos one. Just as
follow:

#include <sys/mman.h>
ptr1=malloc(size1);
.
.
.
ptr2=realloc(ptr1,size2);

...........................

ptr1=malloc(size1);
.
.
.
ptr2=malloc(size2);
memcpy(ptr2,ptr1,size1);
free(ptr1);

Good Luck,

Mehran

realloc

[Chuck Winters]

Hello all,
	Anyone know why a program would freeze at realloc?  I thought
if there was a problem, realloc would just fail.

Thanks,
Chuck

Re: realloc

[Glynn Clements]

Chuck Winters wrote:

> 	Anyone know why a program would freeze at realloc?

By far the most likely reasons are:

a) heap corruption, and
b) passing an invalid pointer (one which wasn't returned from malloc
(or similar), or which has since been freed.

> I thought if there was a problem, realloc would just fail.

If there is insufficient memory to satisfy a request, realloc would
fail.

OTOH, if the heap is corrupt, or if the pointer is invalid, all bets
are off; calling malloc/calloc/realloc/free etc will result in
"undefined behaviour".

-- 
Glynn Clements <glynn.clements@virgin.net>

Re: realloc

[Jason P. Winters]

 
> Hello all,
> 	Anyone know why a program would freeze at realloc?  I thought
> if there was a problem, realloc would just fail.

Not really.  I've had that problem... it's a corrupted heap problem,
usually.  And the results are undefined.. :(

Ciao!

Jason
-- 
|UUCP  jason@txt.com                        Who wills, Can.
|VOICE (408) 243-3425                         Who tries, Does.
|LOCAL Hey, Jason!                              Who loves, Lives.          o_.
|Disclaimer:  Not me! I didn't do *THAT!*                                 <|
|Local Disclaimer:  I'm not here!                   A. McCaffrey           4