Fix division by zero errors and double summary in ping.

2 files changed, 17 insertions, 10 deletions

diff --git a/lib/lib.c b/lib/lib.c
index 6d75e0f3..17a4f483 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -850,14 +850,20 @@ void exit_signal(int sig)
 // adds the handlers to a list, to be called in order.
 void sigatexit(void *handler)
 {
-  struct arg_list *al = xmalloc(sizeof(struct arg_list));
+  struct arg_list *al;
   int i;
 
   for (i=0; signames[i].num != SIGCHLD; i++)
-    signal(signames[i].num, exit_signal);
-  al->next = toys.xexit;
-  al->arg = handler;
-  toys.xexit = al;
+    signal(signames[i].num, handler ? exit_signal : SIG_DFL);
+  if (handler) {
+    al = xmalloc(sizeof(struct arg_list));
+    al->next = toys.xexit;
+    al->arg = handler;
+    toys.xexit = al;
+  } else {
+    llist_traverse(toys.xexit, free);
+    toys.xexit = 0;
+  }
 }
 
 // Convert name to signal number.  If name == NULL print names.
diff --git a/lib/xwrap.c b/lib/xwrap.c
index 26383c92..d5ec9f64 100644
--- a/lib/xwrap.c
+++ b/lib/xwrap.c
@@ -46,12 +46,13 @@ void xexit(void)
 {
   // Call toys.xexit functions in reverse order added.
   while (toys.xexit) {
-    // This is typecasting xexit->arg to a function pointer,then calling it.
-    // Using the invalid signal number 0 lets the signal handlers distinguish
-    // an actual signal from a regular exit.
-    ((void (*)(int))(toys.xexit->arg))(0);
+    struct arg_list *al = llist_pop(&toys.xexit);
 
-    free(llist_pop(&toys.xexit));
+    // typecast xexit->arg to a function pointer, then call it using invalid
+    // signal 0 to let signal handlers tell actual signal from regular exit.
+    ((void (*)(int))(al->arg))(0);
+
+    free(al);
   }
   if (fflush(NULL) || ferror(stdout))
     if (!toys.exitval) perror_msg("write");