[Lcd4linux-devel] My first mail, my first plugin, my fisrt SEGFAULT

[Javi <ja...@gs...>]

Hi list.
It's the first mail I send to the list, so I salute all :)
It's the first time I write a programa for a public project, so please forgive if the code is dirty.

I want to develop a pluging to connect to a MySQL server, execute a query and show on the LCD the number of afected rows.

A very simple C program for doing tha could be like:
---------------------------------------------
#include <mysql/mysql.h>
#include <stdio.h>

int main()
{
	MYSQL *conex;
	MYSQL_RES *result;
	char *consulta = "select * from categories";
	
	mysql_init(conex);
	mysql_real_connect(conex,"192.168.0.12","user","pass","databasename",0,NULL,0);
	mysql_real_query(conex,consulta,(unsigned int) strlen(consulta));
	result=mysql_use_result(conex);
	printf("%d",mysql_field_count(conex));
	mysql_close(conex);
	return 0;
}
---------------------------------------------
That program compiles and runs perfect by itselft on my PC.
The only thing that I should done is just to include that simple program into a plugin. The plugin will be named plugin_sql.c

I've followed the README.plugins and I can copile succesfully my plugin, but when running lcd4linux I can see a "beautifull"
Viloacion de Segmento (which is the spanish term for SEGMENTATION FAULT)

Here is the code. Hope someone could help me. A very sort description of the changes I've made on the plugin_sample.c file is included on the code.
It's only a 50 lines' file so it's very easy to read.

Thanks in advice.

Stolz.
------------------------------------------
/* $Id: plugin_sql.c,v 0.1 2004/03/07 Exp $
 *
 * plugin for exec SQL queries into a MySQL DB.
 *
 * Javier Garcia <ja...@NO...>
 *
 * This file is part of LCD4Linux.
 *
 */

/* 
 * exported functions:
 *
 * int plugin_init_sql (void)
 *  adds various functions
 * Remember to add -lmysqlclient option into Makefile. I.E: CC = gcc -lmysqlclient or run
 * #gcc -I/usr/include/mysql -L/usr/lib/mysql plugin_sql.c -lmysqlclient -o plugin_sql.o
 
 * This is an initial version for testing. my_consulta is basically the mult3 function
 *   included on the plugin_sample.c file. I only added:
 *     #include <mysql/mysql.h> t include the mysql API.
 *     MYSQL *conex; to store the conection data.
 *     Two lines to connect and disconnect to the DBSM.
 *     mysql_init(conex);
 *     mysql_close(conex);
 *
 */

#include <mysql/mysql.h>
// define the include files you need
#include "config.h"

#include <stdlib.h>
#include <string.h>
#include <ctype.h>

// these should always be included
#include "debug.h"
#include "plugin.h"

#ifdef WITH_DMALLOC
#include <dmalloc.h>
#endif

#include <mysql/mysql.h>
#include <stdio.h>

static void my_consulta (RESULT *result, RESULT *arg1)
{
  double value=R2N(arg1)*3.0;
	MYSQL *conex;
// 	MYSQL_RES *result;
// 	MYSQL_ROW fila;
// 	char *consulta = "select * from categories";
// 	int numero;
// 	
 	mysql_init(conex);

// 	mysql_real_connect(conex,"192.168.0.2","myUser","myPass","myDB",0,NULL,0);
// 	mysql_real_query(conex,consulta,(unsigned int) strlen(consulta));
// 	result=mysql_use_result(conex);
// 	numero=mysql_field_count(conex);
// 	printf("%d",numero);

	mysql_close(conex);

  // store result
  SetResult(&result, R_NUMBER, &value); 
}

int plugin_init_sql (void)
{
  AddFunction ("consulta",    1, my_consulta);
  return 0;
}

void plugin_exit_sql(void) 
{
}