Reset the signal mask because apparently the web server sets it to so…

…mething that makes stuff like waitpid() malfunction.

ext/oxt/system_calls.cpp

@@ -42,8 +42,19 @@ interruption_signal_handler(int sig) {
 void
 oxt::setup_syscall_interruption_support() {
 	struct sigaction action;
+	sigset_t signal_set;
 	int ret;
 
+	/* Very important! The signal mask is inherited across fork()
+	 * and exec() and we don't know what the parent process did to
+	 * us. At least on OS X, having a signal mask blocking important
+	 * signals can lead to stuff like waitpid() malfunction.
+	 */
+	sigemptyset(&signal_set);
+	do {
+		ret = sigprocmask(SIG_SETMASK, &signal_set, NULL);
+	} while (ret == -1 && errno == EINTR);
+
 	action.sa_handler = interruption_signal_handler;
 	action.sa_flags   = 0;
 	sigemptyset(&action.sa_mask);

ext/oxt/system_calls.hpp

@@ -102,7 +102,8 @@ namespace oxt {
 	 * Setup system call interruption support.
 	 * This function may only be called once. It installs a signal handler
 	 * for INTERRUPTION_SIGNAL, so one should not install a different signal
-	 * handler for that signal after calling this function.
+	 * handler for that signal after calling this function. It also resets
+	 * the process signal mask.
 	 *
 	 * @warning
 	 * After oxt::setup_syscall_interruption_support() is called, sending a signal