From ddde267b68e184057a12b4875e28f10ba9e69735 Mon Sep 17 00:00:00 2001
From: Rick Myers <rick@jrmyers.net>
Date: Tue, 21 Aug 2018 00:07:23 -0400
Subject: [PATCH] sleeper: handle out of order cont/term signals

---
 sleeper.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 80 insertions(+), 3 deletions(-)

diff --git a/sleeper.c b/sleeper.c
index 637ba60..82b6c67 100644
--- a/sleeper.c
+++ b/sleeper.c
@@ -4,7 +4,21 @@
 #include "str.h"
 #include <unistd.h>
 
+#define SIGQLEN 64
+
+static unsigned int sig_ptr = 0;
+static int sig_queue[SIGQLEN];
+
 static void catch_sig(int sig)
+{
+  int ignored;
+  sig_queue[sig_ptr++] = sig;
+  if (sig_ptr < SIGQLEN) return;
+  ignored = write(1,"increase SIGQLEN\n",17);
+  _exit(2);
+}
+
+static void show_sig(int sig)
 {
   char buf[7+14+2] = "Caught ";
   const char *name;
@@ -27,12 +41,54 @@ static void catch_sig(int sig)
   i += 7;
   buf[i++] = '\n';
   ignored = write(1,buf,i);
-  if (sig != SIGCONT)
-    _exit(1);
 }
 
+static void show_err()
+{
+  int ignored;
+  ignored = write(1,"invalid signal\n",15);
+  _exit(1);
+}
+
+static void show_one(int sig)
+{
+  show_sig(sig);
+  _exit(1);
+}
+
+static void show_two(int sig1, int sig2)
+{
+  show_sig(sig1);
+  show_sig(sig2);
+  _exit(1);
+}
+
+#define new_cont (new_sig == SIGCONT)
+#define new_term (new_sig == SIGTERM)
+#define old_cont (old_sig == SIGCONT)
+#define old_term (old_sig == SIGTERM)
+
+#define state_00 ( ! new_cont && ! new_term && ! old_cont && ! old_term)
+#define state_01 ( ! new_cont && ! new_term && ! old_cont &&   old_term)
+#define state_02 ( ! new_cont && ! new_term &&   old_cont && ! old_term)
+#define state_03 ( ! new_cont && ! new_term &&   old_cont &&   old_term)
+#define state_04 ( ! new_cont &&   new_term && ! old_cont && ! old_term)
+#define state_05 ( ! new_cont &&   new_term && ! old_cont &&   old_term)
+#define state_06 ( ! new_cont &&   new_term &&   old_cont && ! old_term)
+#define state_07 ( ! new_cont &&   new_term &&   old_cont &&   old_term)
+#define state_08 (   new_cont && ! new_term && ! old_cont && ! old_term)
+#define state_09 (   new_cont && ! new_term && ! old_cont &&   old_term)
+#define state_10 (   new_cont && ! new_term &&   old_cont && ! old_term)
+#define state_11 (   new_cont && ! new_term &&   old_cont &&   old_term)
+#define state_12 (   new_cont &&   new_term && ! old_cont && ! old_term)
+#define state_13 (   new_cont &&   new_term && ! old_cont &&   old_term)
+#define state_14 (   new_cont &&   new_term &&   old_cont && ! old_term)
+#define state_15 (   new_cont &&   new_term &&   old_cont &&   old_term)
+
 int main(void)
 {
+  int i, new_sig, old_sig=0;
+
   sig_catch(SIGALRM,catch_sig);
   sig_catch(SIGCONT,catch_sig);
   sig_catch(SIGHUP,catch_sig);
@@ -42,6 +98,27 @@ int main(void)
   sig_catch(SIGUSR1,catch_sig);
   sig_catch(SIGUSR2,catch_sig);
   sig_catch(SIGWINCH,catch_sig);
-  sleep(9999);
+
+  for (i = 0; i < SIGQLEN; ++i) {
+    while (i >= sig_ptr) sleep(9999);
+    new_sig = sig_queue[i];
+    if (i) old_sig = sig_queue[i-1];
+    if (state_00) show_one(new_sig);
+    if (state_01) show_two(old_sig, new_sig);
+    if (state_02) show_two(old_sig, new_sig);
+    if (state_03) show_err();
+    if (state_04) continue;
+    if (state_05) show_one(old_sig);
+    if (state_06) show_two(old_sig, new_sig);
+    if (state_07) show_err();
+    if (state_08) continue;
+    if (state_09) show_two(new_sig, old_sig);
+    if (state_10) show_one(old_sig);
+    if (state_11) show_err();
+    if (state_12) show_err();
+    if (state_13) show_err();
+    if (state_14) show_err();
+    if (state_15) show_err();
+  }
   return 0;
 }