server and multiple clients using pthreads and select() - c++

Question

consider the next piece of code -
int get_ready_connection(int s) {
/* socket of connection */
int caller;
if ((caller = accept(s,NULL,NULL)) < SUCCESS)
{
server_log->write_to_log(sys_call_error(SERVER, "accept"));
return FAILURE;
}
return caller;
}
int establish_connection(sockaddr_in& connection_info)
{
// Create socket
if ((server_sock = socket(AF_INET, SOCK_STREAM, 0)) < SUCCESS)
{
server_log->write_to_log(sys_call_error(SERVER, "socket"));
return FAILURE;
}
// Bind `sock` with given addresses
if (bind(server_sock, (struct sockaddr *) &connection_info, \
sizeof(struct sockaddr_in)) < SUCCESS)
{
close(server_sock);
server_log->write_to_log(sys_call_error(SERVER, "bind"));
return FAILURE;
}
// Max # of queued connects
if (listen(server_sock, MAX_PENDING_CONNECTIONS) < SUCCESS)
{
server_log->write_to_log(sys_call_error(SERVER, "listen"));
return FAILURE;
}
// Create a set of file descriptors and empty it.
fd_set set;
bool is_inside;
int ret_val;
while(true)
{
FD_ZERO(&set);
FD_SET(STDIN_FILENO, &set);
FD_SET(server_sock, &set);
struct timeval tv = {2, 0};
ret_val = select(server_sock + 1, &set, NULL, NULL, &tv); // TODO ret_val
is_inside = FD_ISSET(STDIN_FILENO, &set);
if(is_inside)
{
// get user input
string user_input;
getline(cin, user_input);
if ((strcasecmp(user_input.c_str(), EXIT_TEXT) == 0))
{
return SUCCESS;
}
}
is_inside = FD_ISSET(server_sock, &set);
if(is_inside)
{
// get the first connection request
int current_connection = get_ready_connection(server_sock);
if (current_connection == FAILURE) {
free_allocated_memory();
exit_write_close(server_log, sys_call_error(SERVER, "accept"),
ERROR);
}
// if exit was not typed by the server's stdin, process the request
pthread_t thread;
// create thread
if (pthread_create(&thread, NULL, command_thread_func, &current_connection) != 0)
{
free_allocated_memory();
exit_write_close(server_log, sys_call_error(SERVER, "pthread_create"), ERROR);
}
}
}
}
All im trying to do, is to "listen" to STDIN for the user to type 'EXIT' in server's shell, and to wait for clients to pass commands from their shells (every time a command is recieved by the server from the user, the server parses it, and the server creates a thread that handles execution of the command)
To do it simultaniously, i used select().
When i work with a single thread, everything's perfect. But the problem is when im connecting another client i get a seg fault. i suspect that the problem is right here. any suggestions?

Answer 1

Hard to know if this is your exact problem, but this is definitely a problem:
You can't call pthread_create and provide a pointer to a stack variable (&current_connection) as your thread function's argument. For one thing, it's subject to immediate destruction as soon as the parent exits that scope.
Secondly, it will be overwritten on the next call to get_ready_connection.