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Message-ID: <3E70A394.9080802@liv.ac.uk>
Date: Thu, 13 Mar 2003 15:28:20 +0000
From: Chris Jewell <vs0u8055@liv.ac.uk>
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To: pgsql-interfaces@postgresql.org
Subject: Seg fault on completing query
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    Hi,

I'm working on a frontend to a Postgresql database.  I've chosen C in 
which to work, mainly because I wanted to learn the language.  So, I'm 
using the pqlib frontend library.  The C source I have is below.  I 
compile it (on linux) with gcc -g -Wall -lpq -oantibug antibug.c.  When 
I run the executable, it prints out the query to the screen ok, but also 
prints a "Segmentation Fault" on completion of the list.  Does anyone 
know why? How can I prevent this?

Thanks,

Chris J

Source:

/**************************************************************
 * A test C program to perform a SELECT query on tblantibiotic*
 * on the bugswat database.                                   *
 **************************************************************/

 #include <stdio.h>
 #include <libpq-fe.h>
 #include <stdlib.h>

void exit_nicely(PGconn * conn) {
    PQfinish(conn);
    printf("Abnormal exit");
    exit(1);
}

int main() {
    /* Declare variables for the connection and getting results */
    int num_records;
    PGconn *connect;
    PGresult *res;
    int i;
    char *name;

    /* Connect to the database */
    connect = PQconnectdb("host = linux.chrisdomain dbname=antibugdb 
user=cjewell");
        if (PQstatus(connect) == CONNECTION_BAD) {
            fprintf(stderr, "Could not connect to database");
            fprintf(stderr, "Error: %s\n", PQerrorMessage(connect));
            exit_nicely(connect);
        }

        /* Perform our query */
    res = PQexec(connect, "SELECT * FROM tblactivity;");
        if ((!res) || (PQresultStatus(res) != PGRES_TUPLES_OK)) {
            fprintf(stderr, "SELECT query failed, error: %d\n", 
PQresultStatus(res));
            fprintf(stderr, "Server error: %s\n", PQerrorMessage(connect));
            PQclear(res);
            exit_nicely(connect);
        }

    num_records = PQntuples(res); /* put the number of tuples into 
num_records */

    /* Now print out the results to the screen */
    for(i=0; i < num_records; ++i) {
        sprintf(name, "%s", PQgetvalue(res, i, 0));
        printf("%s\n", name);
    }

    PQclear(res);
    PQfinish(connect);

    return(0);

}


Output:

[cjewell@chris cprogs]$ ./antibug
good
some
poor
none
unknown
Segmentation fault
[cjewell@chris cprogs]$