This page will deal with the  programming in C, C++, Embedded C, JAVA. for Postgres SQL server, Postgres function modules, etc.

When you compile your programs in C or C++, you see this error during execution:

Process terminated by SIGSEGV
core dumped
SYS1808:
The process has stopped. The software diagnostic
code (exception code) is  0005.

This error is caused by pq.dll environment runtime. For solving this problem you can:

1: create a script like psql.cmd; (substutite psql.exe with the name of your application
2: set environment variable PGUSER:
        set pguser=user
user is an user name created by psql monitor with "create user" statement or with createuser.cmd utility

In a network environment you must set the IP workstation in \pgsqldata\pg_hba.conf

File format:
host    dbname    ip_address    address_mask    authtype
For field authtype see pg_hba.conf file in \pgsqldata directory

Example:
host    account    192.168.0.0    255.255.255.0    trust
This example allow all users from 192.168.0.x hosts to connect to account database

Programming Examples:


How compile the "C" programs with postgres:

    gcc -Zcrtdll -I/pgsql/include test1.c -L/pgsql/lib -lpq

The flag -Zcrtdll is necessary because the pq.dll is compiled with the same switch.
-lpq is the library for dynamically linked with pq.dll 
(In the list of library for compiling, pq is the last)

TEST1.C:

 /*
 * testlibpq.c Test the C version of Libpq, the Postgres frontend
 * library.
 *
 *
 */
 #include <stdio.h>
 #include "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 = "template1";

 /* 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); */
 }

How compile the "C++" programs with postgres:

See the examples and makefile  in /pgsql/prog/objc
    gcc -Zcrtdll -I/pgsql/include test1.cc -L/pgsql/lib -lpq++s -lpq -lstdcpp

The flag -Zcrtdll is necessary because the pq.dll is compiled with the   same switch.
-lpq is the library for dynamically linked with pq.dll;
-lpq++s is the library for pq++ code;
-lstdcpp is the library for runtime c++ code
(In the list of library for compiling, this 3 library are the last)

TEST1.CC:

/*-------------------------------------------------------------------------
 *
 * testlibpq0.c--
 *    small test program for libpq++,
 * small interactive loop where queries can be entered interactively
 * and sent to the backend
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    $Header: /pgsql/src/interfaces/libpq++/examples/testlibpq0.cc,v 1.5
      1999/12/03 18:28:32 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

#include <iostream.h>
#include <libpq++.h>

int main()
{
  // Open the connection to the database and make sure it's OK
  PgDatabase data("dbname=template1");
  if ( data.ConnectionBad() ) {
      cout << "Connection was unsuccessful..." << endl
           << "Error message returned: " << data.ErrorMessage() << endl;
      return 1;
  }
  else
      cout << "Connection successful...  Enter queries below:" << endl;

  // Interactively obtain and execute queries
  ExecStatusType status;
  string buf;
  int done = 0;
  while (!done)
    {
      cout << "> ";
      cout.flush();
      getline(cin, buf);
      if ( buf != "" )
               if ( (status = data.Exec( buf.c_str() )) == PGRES_TUPLES_OK )
                  data.DisplayTuples();
               else
                  cout << "No tuples returned..." << endl
                       << "status = " << status << endl
                       << "Error returned: " << data.ErrorMessage() << endl;
      else
               done = 1;
      }
  return 0;
} // End main()