cgi: tidy up fastcgi_cleanup signal handler (#13026)

* signal handlers can only touch global volatile sig_atomic_t variables.
* fastcgi_cleanup is static
* structs sigaction are static
* A signal handler cannot call exit() because it is not async signal safe,
  call _exit instead.

Author: crrodriguez

sapi/cgi/cgi_main.c

@@ -97,7 +97,7 @@ int __riscosify_control = __RISCOSIFY_STRICT_UNIX_SPECS;
 
 #ifndef PHP_WIN32
 /* XXX this will need to change later when threaded fastcgi is implemented.  shane */
-struct sigaction act, old_term, old_quit, old_int;
+static struct sigaction act, old_term, old_quit, old_int;
 #endif
 
 static void (*php_php_import_environment_variables)(zval *array_ptr);
@@ -116,7 +116,7 @@ static int parent = 1;
 
 #ifndef PHP_WIN32
 /* Did parent received exit signals SIG_TERM/SIG_INT/SIG_QUIT */
-static int exit_signal = 0;
+static volatile sig_atomic_t exit_signal = 0;
 
 /* Is Parent waiting for children to exit */
 static int parent_waiting = 0;
@@ -1454,7 +1454,7 @@ static void init_request_info(fcgi_request *request)
 /**
  * Clean up child processes upon exit
  */
-void fastcgi_cleanup(int signal)
+static void fastcgi_cleanup(int signal)
 {
 #ifdef DEBUG_FASTCGI
 	fprintf(stderr, "FastCGI shutdown, pid %d\n", getpid());
@@ -1468,7 +1468,7 @@ void fastcgi_cleanup(int signal)
 	if (parent && parent_waiting) {
 		exit_signal = 1;
 	} else {
-		exit(0);
+		_exit(0);
 	}
 }
 #else