Thread: C & C ++Program Problem

C & C ++Program Problem

From
Arindam Haldar
Date:
hi all,
am trying to use C & C++ libraries with postgresql 7.2.
while compiling a sample programe(attached) there were thse errors
encounterd !..

[arindam@my src]$
[arindam@my src]$ gcc egTry.c
/tmp/ccTLiExh.o: In function `main':
/tmp/ccTLiExh.o(.text+0x12): undefined reference to `PQconnectdb'
/tmp/ccTLiExh.o(.text+0x2b): undefined reference to `PQstatus'
/tmp/ccTLiExh.o(.text+0x5c): undefined reference to `PQerrorMessage'
/tmp/ccTLiExh.o(.text+0xac): undefined reference to `PQexec'
/tmp/ccTLiExh.o(.text+0xc5): undefined reference to `PQresultStatus'
/tmp/ccTLiExh.o(.text+0xf3): undefined reference to `PQclear'
/tmp/ccTLiExh.o(.text+0x104): undefined reference to `PQfinish'
/tmp/ccTLiExh.o(.text+0x12e): undefined reference to `PQntuples'
/tmp/ccTLiExh.o(.text+0x159): undefined reference to `PQgetvalue'
/tmp/ccTLiExh.o(.text+0x186): undefined reference to `PQclear'
/tmp/ccTLiExh.o(.text+0x197): undefined reference to `PQfinish'
collect2: ld returned 1 exit status
[arindam@my src]$

lib & include dir are in /usr/lib/pgsql-7.2 & /usr/include/pgsql-7.2.
i have tried to compliethis programme with RH7.2(with postgres rpm & a
configured from tar file)..
i need help pls...   i want to use C or C++
thanking u in advance
A.H
/*
 * testlibpq.c Test the C version of Libpq, the Postgres frontend
 * library.
 * Sample Program 1
 */
#include <stdio.h>
#include <pgsql-7.2/libpq-fe.h>

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

main()
{
    char       *pghost,
               *pgport,
               *pgoptions,
               *pgtty;
    char       *dbName;
    int         nFields;
    int         i,
                j;

    /* FILE *debug; */

    PGconn     *conn;
    PGresult   *res;

    /*
     * begin, by setting the parameters for a backend connection if the
     * parameters are null, then the system will try to use reasonable
     * defaults by looking up environment variables or, failing that,
     * using hardwired constants
     */
    pghost = NULL;              /* host name of the backend server */
    pgport = NULL;              /* port of the backend server */
    pgoptions = NULL;           /* special options to start up the backend
                                 * server */
    pgtty = NULL;               /* debugging tty for the backend server */
    dbName = "masterdb";

    /* make a connection to the database */
    conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);

    /*
     * check to see that the backend connection was successfully made
     */
    if (PQstatus(conn) == CONNECTION_BAD)
    {
        fprintf(stderr, "Connection to database '%s' failed.\n", dbName);
        fprintf(stderr, "%s", PQerrorMessage(conn));
        exit_nicely(conn);
    }

    /* debug = fopen("/tmp/trace.out","w"); */
    /* PQtrace(conn, debug);  */

    /* start a transaction block */
    res = PQexec(conn, "BEGIN");
    if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
    {
        fprintf(stderr, "BEGIN command failed\n");
        PQclear(res);
        exit_nicely(conn);
    }

    /*
     * should PQclear PGresult whenever it is no longer needed to avoid
     * memory leaks
     */
    PQclear(res);

    /*
     * fetch instances from the pg_database, the system catalog of
     * databases
     */
    res = PQexec(conn, "DECLARE mycursor CURSOR FOR select * from pg_database");
    if (!res || PQresultStatus(res) != PGRES_COMMAND_OK)
    {
        fprintf(stderr, "DECLARE CURSOR command failed\n");
        PQclear(res);
        exit_nicely(conn);
    }
    PQclear(res);
    res = PQexec(conn, "FETCH ALL in mycursor");
    if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        fprintf(stderr, "FETCH ALL command didn't return tuples properly\n");
        PQclear(res);
        exit_nicely(conn);
    }

    /* first, print out the attribute names */
    nFields = PQnfields(res);
    for (i = 0; i < nFields; i++)
        printf("%-15s", PQfname(res, i));
    printf("\n\n");

    /* next, print out the instances */
    for (i = 0; i < PQntuples(res); i++)
    {
        for (j = 0; j < nFields; j++)
            printf("%-15s", PQgetvalue(res, i, j));
        printf("\n");
    }
    PQclear(res);

    /* close the cursor */
    res = PQexec(conn, "CLOSE mycursor");
    PQclear(res);

    /* commit the transaction */
    res = PQexec(conn, "COMMIT");
    PQclear(res);

    /* close the connection to the database and cleanup */
    PQfinish(conn);

    /* fclose(debug); */
    return 0;

}


Re: C & C ++Program Problem

From
Martijn van Oosterhout
Date:
On Thu, May 16, 2002 at 04:07:38AM +0530, Arindam Haldar wrote:
> hi all,
> am trying to use C & C++ libraries with postgresql 7.2.
> while compiling a sample programe(attached) there were thse errors
> encounterd !..
>
> [arindam@my src]$
> [arindam@my src]$ gcc egTry.c

Try: gcc egTry.c -lpq

(or is it -lpg?)

The compiler needs to know which library contains the symbols you're
missing.

HTH,
--
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Canada, Mexico, and Australia form the Axis of Nations That
> Are Actually Quite Nice But Secretly Have Nasty Thoughts About America

Re: C & C ++Program Problem

From
Arindam Haldar
Date:
hi,
thanx for the hint. am re-entering c programming from DOS world !--my
apologies as am again a learner. 1 more Query on to this.
POstgres-7.2 was not configured with-->--with-gnu-ld , which i just saw
is default set to no... So can that be problem while compling C & C++
prorgrames ?
thanx again in advance for ur help.
A.H

Nigel J. Andrews wrote:


You need to read the error messages. It's not a postgres issue it's a
linking
issue. Try giving the -lpq flag to gcc.

On Thu, 16 May 2002, Arindam Haldar wrote:

hi all,
am trying to use C & C++ libraries with postgresql 7.2.
while compiling a sample programe(attached) there were thse errors
encounterd !..

[arindam@my src]$
[arindam@my src]$ gcc egTry.c
/tmp/ccTLiExh.o: In function `main':
/tmp/ccTLiExh.o(.text+0x12): undefined reference to `PQconnectdb'
/tmp/ccTLiExh.o(.text+0x2b): undefined reference to `PQstatus'
/tmp/ccTLiExh.o(.text+0x5c): undefined reference to `PQerrorMessage'
/tmp/ccTLiExh.o(.text+0xac): undefined reference to `PQexec'
/tmp/ccTLiExh.o(.text+0xc5): undefined reference to `PQresultStatus'
/tmp/ccTLiExh.o(.text+0xf3): undefined reference to `PQclear'
/tmp/ccTLiExh.o(.text+0x104): undefined reference to `PQfinish'
/tmp/ccTLiExh.o(.text+0x12e): undefined reference to `PQntuples'
/tmp/ccTLiExh.o(.text+0x159): undefined reference to `PQgetvalue'
/tmp/ccTLiExh.o(.text+0x186): undefined reference to `PQclear'
/tmp/ccTLiExh.o(.text+0x197): undefined reference to `PQfinish'
collect2: ld returned 1 exit status
[arindam@my src]$

lib & include dir are in /usr/lib/pgsql-7.2 & /usr/include/pgsql-7.2.
i have tried to compliethis programme with RH7.2(with postgres rpm & a
configured from tar file)..
i need help pls...   i want to use C or C++
thanking u in advance
A.H


Re: [INTERFACES] C & C ++Program Problem

From
jtv
Date:
On Thu, May 16, 2002 at 04:07:38AM +0530, Arindam Haldar wrote:

> am trying to use C & C++ libraries with postgresql 7.2.
> while compiling a sample programe(attached) there were thse errors
> encounterd !..

Are you linking your program with libpq?  It would seem that this may
not be the case, but you need to.


Jeroen