Bug #16204 When I do an special query to an embedded DB using a thread, it makes segfault
Submitted: 4 Jan 2006 21:07 Modified: 5 Jan 2006 20:15
Reporter: Emiliano Marino Email Updates:
Status: Not a Bug Impact on me:
Category:MySQL Server: Embedded Library ( libmysqld ) Severity:S1 (Critical)
Version:4.1.14 OS:Linux (Debian Linux)
Assigned to: CPU Architecture:Any

[4 Jan 2006 21:07] Emiliano Marino
When you create a thread that's indirectly call's to mysql_query() funtion with an specifical SQL Select to access and connected embedded database, the programs causes segmentation fault.

We tryed doing it with fork, and it worked ok. The problem looks like is with threads.

We test this program on I386 and ARM arquitectures, and fail in the same way.

Some help would be apreciated.

How to repeat:
Compile and Run this:

#include <pthread.h>
#include <dlfcn.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <mysql.h>

#define DEFAULT_QUERY "SELECT DISTINCT varCounter FROM HistoricFlowHourly WHERE (varCounter MOD 35) = 1"
#define DB_NAME "myefm"
#define DB_HOST "localhost"
#define DB_USER "root"
#define DB_PASS NULL

int startMysql();
int closeMysql();
void *doQuery(void *query);

MYSQL *db;

const char *server_groups[] = {"embedded", "server", NULL};

char *server_args[] = {"nada","--defaults-file=/etc/my.cnf"};

int main (int argc, char **argv) {
	void *status;
	pthread_t tHandle;
	char *query, aux[300];
	printf("Starting Mysql engine...\n");
	if (argc < 2) {
		printf("No args, using default query...\n");
		query = aux;
	else {
		query = argv[1];
	if (pthread_create(&tHandle, NULL, doQuery, (void *) query)) {
		printf("Error: Failed to create thread.\n");
		return 1;
	pthread_join(tHandle, &status);
	printf("Stopping Mysql...\n");	
	printf("That's all folks...\n");
	return 0;

int startMysql() {
	mysql_server_init(sizeof(server_args)/sizeof(char *),server_args,(char**)server_groups);
	db = mysql_init(NULL);
	if (!mysql_real_connect(db, DB_HOST, DB_USER, DB_PASS, DB_NAME, 0, NULL, 0)) {
		printf("Connection to Mysql failed...\n");
		return 1;
	return 0;

int closeMysql() {
	return 0;

void *doQuery(void *query) {
	MYSQL_RES *resultSet;
	int fieldCount = 0, field = 0, count = 0, rowCount = 0;
	printf("Sending query: [%s].\n",(char *) query);

	if (mysql_query(db,(char *) query)) {
		printf("Error: %s\n",mysql_error(db));
		return NULL;
	printf("Query Success...\n");
	if (mysql_field_count(db) > 0) {
		MYSQL_ROW rows;
		if (!(resultSet = mysql_store_result(db))) {
			printf("Error: %s\n",mysql_error(db));
			return NULL;
		fieldCount = mysql_num_fields(resultSet);
		while ((rows = mysql_fetch_row(resultSet))) {
			for (field = 0; field < fieldCount; field++) {
				if ((char *) *rows) {
					printf("%s ",(char *) *rows);
				else {
					printf("(null) ");
	else {
		printf("Affected rows [%ld]",(long) mysql_affected_rows(db));
		return NULL;
	rowCount = mysql_num_rows(resultSet);
	printf("rowCount = [%d].\n",rowCount);
	return NULL;

Suggested fix:
don't have a clue.
[5 Jan 2006 14:50] Emiliano Marino
Correcting category.
[5 Jan 2006 20:15] Emiliano Marino
I'm sorry to bother with this... it was not a bug just an couple of ignorant people. The solution: Put mysql_thread_init at start and mysql_thread_end at the end :-D

We are trying this... i should work. :P

So sorry for the inconvenience.