Use ev_signal to avoid async-unsafe functions (Thanks Markus)

Functions such as fprintf() might be unsafe to use in a signal handler,
see http://stackoverflow.com/questions/3941271/#answer-3941563

By using ev_signal, libev will use a tiny signal handler which just
passes on the information and then calls (outside of the signal handler)
our callback function which can use fprintf() and other unsafe
functions.

fixes #803

diff --git a/src/main.c b/src/main.c
index 8bae9957db894e3fac02363b37e857ef49f9ad4f..a4bd1b9ba37aee2b65a217273be2389aba5cda6c 100644 (file)
--- a/src/main.c
+++ b/src/main.c
@@ -232,13 +232,15 @@ static void i3_exit(void) {
  * Unlinks the SHM log and re-raises the signal.
  *
  */
-static void handle_signal(int sig, siginfo_t *info, void *data) {
+static void handle_signal(struct ev_loop *loop, ev_signal *w, int revents) {
+    int sig = w->signum;
     fprintf(stderr, "Received signal %d, terminating\n", sig);
     if (*shmlogname != '\0') {
         fprintf(stderr, "Closing SHM log \"%s\"\n", shmlogname);
         shm_unlink(shmlogname);
     }
     fflush(stderr);
+    ev_signal_stop(loop, w);
     raise(sig);
 }
 
@@ -780,31 +782,32 @@ int main(int argc, char *argv[]) {
     }
     xcb_ungrab_server(conn);
 
-    struct sigaction action;
 
-    action.sa_sigaction = handle_signal;
-    action.sa_flags = SA_NODEFER | SA_RESETHAND | SA_SIGINFO;
-    sigemptyset(&action.sa_mask);
+#define HANDLE_SIGNAL_EV(signum) \
+    do { \
+        struct ev_signal *signal_watcher = scalloc(sizeof(struct ev_signal)); \
+        ev_signal_init(signal_watcher, handle_signal, signum); \
+        ev_signal_start(main_loop, signal_watcher); \
+    } while (0)
 
     if (!disable_signalhandler)
         setup_signal_handler();
     else {
         /* Catch all signals with default action "Core", see signal(7) */
-        if (sigaction(SIGQUIT, &action, NULL) == -1 ||
-            sigaction(SIGILL, &action, NULL) == -1 ||
-            sigaction(SIGABRT, &action, NULL) == -1 ||
-            sigaction(SIGFPE, &action, NULL) == -1 ||
-            sigaction(SIGSEGV, &action, NULL) == -1)
-            ELOG("Could not setup signal handler");
+        HANDLE_SIGNAL_EV(SIGQUIT);
+        HANDLE_SIGNAL_EV(SIGILL);
+        HANDLE_SIGNAL_EV(SIGABRT);
+        HANDLE_SIGNAL_EV(SIGFPE);
+        HANDLE_SIGNAL_EV(SIGSEGV);
     }
 
     /* Catch all signals with default action "Term", see signal(7) */
-    if (sigaction(SIGHUP, &action, NULL) == -1 ||
-        sigaction(SIGINT, &action, NULL) == -1 ||
-        sigaction(SIGALRM, &action, NULL) == -1 ||
-        sigaction(SIGUSR1, &action, NULL) == -1 ||
-        sigaction(SIGUSR2, &action, NULL) == -1)
-        ELOG("Could not setup signal handler");
+    HANDLE_SIGNAL_EV(SIGHUP);
+    HANDLE_SIGNAL_EV(SIGINT);
+    HANDLE_SIGNAL_EV(SIGALRM);
+    HANDLE_SIGNAL_EV(SIGTERM);
+    HANDLE_SIGNAL_EV(SIGUSR1);
+    HANDLE_SIGNAL_EV(SIGUSR2);
 
     /* Ignore SIGPIPE to survive errors when an IPC client disconnects
      * while we are sending him a message */