persistent variables between cross-calls in C functions

Dear all:

I could not find any way to store a value in a C function
between calls.

For example, the following function doesn't work as expected:

#include "postgres.h"
#include "fmgr.h"

PG_FUNCTION_INFO_V1(next_value);

Datum
next_value(PG_FUNCTION_ARGS)
{
static int n;
PG_RETURN_INT32(n);
n++;
}

select next_value();
will always return 0;

even if I declare n as a global variable outside the fucntion.

Thanks a lot.

Fabio Furia Silva

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