# HG changeset patch
# User jbe
# Date 1497731744 -7200
# Node ID ce109800ae2dd5ae7ff32ae0f32dd083e7d0246b
# Parent  1eef86d3b9255ee107045832692d813739d2f7ca
Extend moonbridge_io.poll(...) to support waiting for child process termination

diff -r 1eef86d3b925 -r ce109800ae2d moonbridge_io.c
--- a/moonbridge_io.c	Sat Jun 17 20:07:03 2017 +0200
+++ b/moonbridge_io.c	Sat Jun 17 22:35:44 2017 +0200
@@ -1657,6 +1657,7 @@
 static int moonbr_io_poll(lua_State *L) {
   moonbr_io_handle_t *handle;
   moonbr_io_listener_t *listener;
+  moonbr_io_child_t *child;
   int fd, isnum;
   int nfds = 0;
   fd_set readfds, writefds, exceptfds;
@@ -1664,6 +1665,8 @@
   int force_wakeup = 0;
   int use_timeout = 0;  // negative for negative timeout
   int check_sigterm = 0;
+  int check_child = 0;
+  int childstatus;
   sigset_t mask, orig_mask;
   int status;
   FD_ZERO(&readfds);
@@ -1693,8 +1696,20 @@
             fd = listener->fd;
             if (fd < 0) luaL_error(L, "Attempt to poll a closed listener");
           } else {
-            fd = lua_tointegerx(L, -2, &isnum);
-            if (!isnum) luaL_error(L, "Expected integer (file descriptor), I/O handle, or listener in table key");
+            child = luaL_testudata(L, -2, MOONBR_IO_CHILD_MT_REGKEY);
+            if (child) {
+              check_child = 1;
+              if (waitpid(child->pid, &childstatus, WNOHANG|WNOWAIT) != -1) {
+                force_wakeup = 1;
+              } else if (errno != ECHILD && errno != EINTR) {
+                moonbr_io_prepare_errmsg();
+                luaL_error(L, "Error in waitpid call: %s", errmsg);
+              }
+              continue;
+            } else {
+              fd = lua_tointegerx(L, -2, &isnum);
+              if (!isnum) luaL_error(L, "Expected integer (file descriptor), I/O handle, or listener in table key");
+            }
           }
         }
         if (fd < 0 || fd >= FD_SETSIZE) luaL_error(L, "File descriptor out of valid range");
@@ -1743,20 +1758,29 @@
   if (use_timeout < 0) force_wakeup = 1;
   if (!lua_isnoneornil(L, 4)) luaL_checktype(L, 4, LUA_TBOOLEAN);
   check_sigterm = lua_toboolean(L, 4);
-  if (check_sigterm) {
+  if ((check_sigterm || check_child) && !force_wakeup) {
+    sigemptyset(&mask);
+    if (check_sigterm) sigaddset(&mask, SIGTERM);
+    if (check_child) sigaddset(&mask, SIGCHLD);
+    if (sigprocmask(SIG_BLOCK, &mask, &orig_mask)) abort();
+  }
+  if (check_sigterm && moonbr_io_sigterm_flag) {
     if (!force_wakeup) {
-      sigemptyset(&mask);
-      sigaddset(&mask, SIGTERM);
-      if (sigprocmask(SIG_BLOCK, &mask, &orig_mask)) abort();
+      if (sigprocmask(SIG_SETMASK, &orig_mask, NULL)) abort();
     }
-    if (moonbr_io_sigterm_flag) {
-      if (!force_wakeup) {
-        if (sigprocmask(SIG_SETMASK, &orig_mask, NULL)) abort();
-      }
-      lua_pushboolean(L, 0);
-      lua_pushliteral(L, "SIGTERM received");
-      lua_pushboolean(L, 1);
-      return 3;
+    lua_pushboolean(L, 0);
+    lua_pushliteral(L, "SIGTERM received");
+    lua_pushboolean(L, 1);
+    return 3;
+  }
+  if (check_child && !force_wakeup) {
+    if (wait3(&childstatus, WNOHANG|WNOWAIT, NULL) != -1) {
+      if (sigprocmask(SIG_SETMASK, &orig_mask, NULL)) abort();
+      force_wakeup = 1;
+    } else if (errno != ECHILD && errno != EINTR) {
+      moonbr_io_prepare_errmsg();
+      if (sigprocmask(SIG_SETMASK, &orig_mask, NULL)) abort();
+      luaL_error(L, "Error in waitpid call: %s", errmsg);
     }
   }
   if (use_timeout < 0) {
diff -r 1eef86d3b925 -r ce109800ae2d reference.txt
--- a/reference.txt	Sat Jun 17 20:07:03 2017 +0200
+++ b/reference.txt	Sat Jun 17 22:35:44 2017 +0200
@@ -310,7 +310,7 @@
 
 ### moonbridge_io.exec(command, arg1, arg2, ...)
 
-Executes the given command and returns a handle with three sockets named
+Executes the given command and returns a child handle with three sockets named
 "stdin", "stdout", and "stderr" as well as the following methods:
 
 - :kill(signal)
@@ -335,6 +335,9 @@
 
 The method :wait_yield() is an alias for :wait_call(coroutine.yield).
 
+It is possible to wait for process termination by including the child handle
+in the input_set of the moonbridge_io.poll(...) call.
+
 moonbridge_io.exec(...) returns nil (as first return value) plus an error
 message (as second return value) in case of error.
 
@@ -399,6 +402,9 @@
 which does evaluate to true, e.g. input_set = {[socketA] = true}. If a set is
 nil, it is treated as being empty.
 
+The input_set may also contain listeners (to wait for incoming connections) and
+child handles (to wait for process termination).
+
 If the 4th parameter (wakeup_on_sigterm) is set to true, then the function
 returns immediately if the process received at least one SIGTERM signal after
 moonbridge_io.catch_sigterm() has been called for the first time. Three values