extending by using procedurallanguage C : problems accessing shared memory

Hi,

I'm having some trouble extending postgresql with some C-functions.

Although I have done some tests with examples that work fine  I have
trouble in a function in which I wat to access data that is in shared
memory.

Functionalty is split into 2 functions because the ti_shmmav fuction is
also used by other programs.

Trouble is in the second function where I use the shmat call .  Is there
a way to do this ?

When running :

select shmmav(2785298, 1);        // the large number is the segment id

I get the following message:

server closed the connection unexpectedly
      This probably means the server terminated abnormally
      before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.

* There is data in the shared memory and I've tested it using a
perlscript to perform the same kind of operation

Some hints would be very helpful,

thanks ,

Feite Brekeveld
----------------------code snippet
--------------------------------------------

double *shmmav(int *shmid, int *period)
{
double *ret = palloc(sizeof(double));

*ret = ti_shmmav(shmid , period);
return ret;
}


double ti_shmmav(int *shmid, int *period)
{
double ret;
PREC *pprec;
int i = 0;
double total = 0.0;

pprec = (PREC *)shmat( *shmid, NULL, SHM_RDONLY);
if ( pprec == NULL) {
                fprintf(stderr, "Error attaching SHM: id %d\n", *shmid);
}
while (i < *period) {
    total += pprec[i].c;
    i++;
}

ret = total / (float)(*period);
shmdt(pprec);

return ret;
}

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