I need to execute clean up functions in SIGINT handler, but I can't pass local data to it. Here an example:
int main(int argc, char *argv[]) {
struct database *db = db_cursor();
sockfd_t master_socket = init_server();
signal(SIGINT, sigint_handler);
while (1) {
// accepting connections
}
}
void sigint_handler(int s) {
destroy_db(db);
shutdown(master_socket, SHUT_RDWR);
close(master_socket);
exit(EXIT_SUCCESS);
}
How can I implement such behaviour? I've tried make this variables are global, but
I can't invoke this functions at compile time (error: initializer element is not a compile-time constant).
Only a very limited number of functions is guaranteed to be async-signal-safe and therefore may be called from within a signal handler, exit() f.e. does not belong to them.
Take a different approach:
#include <signal.h>
volatile sig_atomic_t sigint_received = 0; /* volatile might be necessary depending on
the system/implementation in use.
(see "C11 draft standard n1570: 5.1.2.3")*/
void sigint_handler(int s)
{
sigint_received = 1;
}
int main(void)
{
signal(SIGINT, sigint_handler);
while (!sigint_received)
{
/* Do stuff. */
}
/* Clean up here. */
}
For more on this see
- the Linux man-page here
man 7 signal
- the POSIX specifications here.
Note: To be maximal portable you want to use sigaction() instead of signal().
The code to replace signal() might look like this:
struct sigaction sa =
{
sigint_handler
/*, SA_RESTART */ /* Set this by if blocking calls like read() or accept()
should _not_ return on signal reception. */
};
if (-1 == sigaction(SIGINT, &sa, NULL))
{
perror("sigaction() failed");
exit(EXIT_FAILURE);
}
Documentation on sigaction():
