Hello,

when csoundDestroy is called to destroy an instance of Csound, the memory used by the struct CSOUND_ pointed by the CSOUND pointer is freed (line 1198 in csound.c).

But the pointer itself still points to this memory. If the operating system does not realloc this memory, there's a potential danger. You can see this by running the example below:

#include <csound/csound.h>

int main(int argc, char *argv[])
{
  CSOUND *csound = csoundCreate(NULL);
  printf("%d\n", (int)csoundGetSr(csound));
  csoundDestroy(csound);
  sleep(10);
  printf("%d\n", (int)csoundGetKr(csound));
}

Normally, the last statement should cause a segfault. On my system, it happily prints 4410 and then the program silently returns.

We could change the csoundDestroy signature to csoundDestroy(CSOUND **) so that the procedure can erase the CSOUND pointer when the memory is freed. But this would break backward compatibility. Another solution would be to have a self reference to the struct CSOUND_ at the end of the private data part of the structure. This self-reference would be initialized in csoundCreate and csoundDestroy could use it to erase the opaque pointer.

What do you think?

Francois

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Hi François,

can you submit a ticket on this? Then we can keep track of it and decide what to do (before the release).
This seems to be an issue that has been there since 2004-5, and we have not yet seen it  as a cause of problems,
but let's review it.

Thanks.

Regards

Victor

On 14 May 2013, at 15:30, Francois PINOT wrote:

> Hello,
>
> when csoundDestroy is called to destroy an instance of Csound, the memory used by the struct CSOUND_ pointed by the CSOUND pointer is freed (line 1198 in csound.c).
> But the pointer itself still points to this memory. If the operating system does not realloc this memory, there's a potential danger. You can see this by running the example below:
>
> #include <csound/csound.h>
>
> int main(int argc, char *argv[])
> {
>   CSOUND *csound = csoundCreate(NULL);
>   printf("%d\n", (int)csoundGetSr(csound));
>   csoundDestroy(csound);
>   sleep(10);
>   printf("%d\n", (int)csoundGetKr(csound));
> }
>
> Normally, the last statement should cause a segfault. On my system, it happily prints 4410 and then the program silently returns.
>
> We could change the csoundDestroy signature to csoundDestroy(CSOUND **) so that the procedure can erase the CSOUND pointer when the memory is freed. But this would break backward compatibility. Another solution would be to have a self reference to the struct CSOUND_ at the end of the private data part of the structure. This self-reference would be initialized in csoundCreate and csoundDestroy could use it to erase the opaque pointer.
>
> What do you think?
>
> Francois

> ------------------------------------------------------------------------------
> AlienVault Unified Security Management (USM) platform delivers complete
> security visibility with the essential security capabilities. Easily and
> efficiently configure, manage, and operate all of your security controls
> from a single console and one unified framework. Download a free trial.
> http://p.sf.net/sfu/alienvault_d2d_______________________________________________
> Csound-devel mailing list
> Csound-devel@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/csound-devel

Dr Victor Lazzarini
Senior Lecturer
Dept. of Music
NUI Maynooth Ireland
tel.: +353 1 708 3545
Victor dot Lazzarini AT nuim dot ie

------------------------------------------------------------------------------
AlienVault Unified Security Management (USM) platform delivers complete
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efficiently configure, manage, and operate all of your security controls
from a single console and one unified framework. Download a free trial.
http://p.sf.net/sfu/alienvault_d2d
_______________________________________________
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