[GENERAL] Error loading trigger in C

[Juan Jose Costello Levien]

Hello,
I am trying to use a trigger function I wrote in C. Basically what I 
want to do is to audit a table when a row is inserted into another table 
by copying the row to the new table. It compiles Ok and I created a 
shared library trigger.so. But when I load it into pgAdmin it tells me 
'An error had occured'.

To address that I put here the source code so you can check it out:
(note: it has a oid (blob) field the row, and that could be a problem 
for the query syntax, maybe there is the error)

#include "postgres.h"
#include "executor/spi.h" /* SPI */
#include "commands/trigger.h" /* triggers */
#include <stdlib.h>
#include <string.h>
extern Datum trigf(PG_FUNCTION_ARGS);
PG_FUNCTION_INFO_V1(trigf);
Datum
trigf(PG_FUNCTION_ARGS)
{
   char * query = (char *)malloc(sizeof(char *)*500);
   TriggerData *trigdata = (TriggerData *) fcinfo->context;
   TupleDesc tupdesc;
   HeapTuple rettuple;
   char *when;
   bool checknull = false;
   bool isnull;
   int ret, i;
/* aquí nos aseguramos que se llama a la función como un trigger*/
if (!CALLED_AS_TRIGGER(fcinfo))
   elog(ERROR, "trigf: no se llamó por el administrador de triggers");
/* datos que devuelve el ejecutor */
if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
   rettuple = trigdata->tg_newtuple;
else
   rettuple = trigdata->tg_trigtuple;
/* chequeo de valores nulos */
if (!TRIGGER_FIRED_BY_DELETE(trigdata->tg_event)
&& TRIGGER_FIRED_BEFORE(trigdata->tg_event))
   checknull = true;
if (TRIGGER_FIRED_BEFORE(trigdata->tg_event))
   when = "antes";
else
   when = "después";
tupdesc = trigdata->tg_relation->rd_att;
/* conexión al SPI (Server Programming Interface) */
if ((ret = SPI_connect()) < 0)
   elog(INFO, "trigf (disparado %s): SPI_connect devolvió %d", when, ret);
/* ejecuto el query para insertar en la tabla de auditoría */
strcpy(query, "INSERT INTO visita_log VALUES ('");
strcat(query, trigdata->tg_trigger->tgargs[0]);
strcat(query, "','");
strcat(query, trigdata->tg_trigger->tgargs[1]);
strcat(query, "','");
strcat(query, trigdata->tg_trigger->tgargs[2]);
strcat(query, "','");
strcat(query, trigdata->tg_trigger->tgargs[3]);
strcat(query, "',");
strcat(query, trigdata->tg_trigger->tgargs[4]);
strcat(query, ",'");
strcat(query, trigdata->tg_trigger->tgargs[5]);
strcat(query, "');");
SPI_exec(query, 0);
/* count(*) devuelve int8, cuidado con la conversión */
i = DatumGetInt64(SPI_getbinval(SPI_tuptable->vals[0],
       SPI_tuptable->tupdesc,
       1,
       &isnull));
elog (INFO, "trigf (disparado %s): hay %d filas en la tabla", when, i);
SPI_finish();
if (checknull)
{
   SPI_getbinval(rettuple, tupdesc, 1, &isnull);
   if (isnull)
       rettuple = NULL;
}
return PointerGetDatum(rettuple);
}
// End of source code
I use PostgreSQL 7.4.1 and Mandrake 10.
The compiler sequence I used is:
gcc -I "./" -fpic -c trigger.c
gcc -I "./" -shared -o trigger.so trigger.o
and when I include it in Trigger functions pgAdmin complains with "An 
error had occured" (and says nothing). What I am doing wrong?

Thanks in advance.
Juan
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