bug#17172: 24.3.50; Timeouts when pasting from mouse

[Paul Eggert <eggert@cs.ucla.edu>]

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Thanks for the bug report.  I can't reproduce the problem on my Fedora 
20 x86-64 desktop, but in reviewing xgselect.c I see some glitches that 
could explain things.  Please try the attached patch and let us know 
whether it helps with your problem.  Please compile with 
-DENABLE_CHECKING so that the patch's 'eassert' calls have teeth.  Thanks.

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=== modified file 'src/xgselect.c'
--- src/xgselect.c	2014-03-05 06:31:57 +0000
+++ src/xgselect.c	2014-04-15 07:52:04 +0000
@@ -33,16 +33,15 @@
 xg_select (int fds_lim, fd_set *rfds, fd_set *wfds, fd_set *efds,
 	   struct timespec const *timeout, sigset_t const *sigmask)
 {
-  fd_set all_rfds, all_wfds;
+  fd_set all_rfds, all_wfds, all_efds;
   struct timespec tmo;
   struct timespec const *tmop = timeout;
 
   GMainContext *context;
-  int have_wfds = wfds != NULL;
   GPollFD gfds_buf[128];
   GPollFD *gfds = gfds_buf;
   int gfds_size = sizeof gfds_buf / sizeof *gfds_buf;
-  int n_gfds, retval = 0, our_fds = 0, max_fds = fds_lim - 1;
+  int n_gfds, retval = 0, all_lim = fds_lim;
   int i, nfds, tmo_in_millisec;
   bool need_to_dispatch;
   USE_SAFE_ALLOCA;
@@ -59,6 +58,8 @@
   else FD_ZERO (&all_rfds);
   if (wfds) all_wfds = *wfds;
   else FD_ZERO (&all_wfds);
+  eassert (!efds);
+  FD_ZERO (&all_efds);
 
   n_gfds = g_main_context_query (context, G_PRIORITY_LOW, &tmo_in_millisec,
 				 gfds, gfds_size);
@@ -71,19 +72,28 @@
     }
 
   for (i = 0; i < n_gfds; ++i)
-    {
-      if (gfds[i].events & G_IO_IN)
-        {
-          FD_SET (gfds[i].fd, &all_rfds);
-          if (gfds[i].fd > max_fds) max_fds = gfds[i].fd;
-        }
-      if (gfds[i].events & G_IO_OUT)
-        {
-          FD_SET (gfds[i].fd, &all_wfds);
-          if (gfds[i].fd > max_fds) max_fds = gfds[i].fd;
-          have_wfds = 1;
-        }
-    }
+    if (gfds[i].events & (G_IO_IN | G_IO_OUT | G_IO_PRI))
+      {
+	int fd = gfds[i].fd;
+	eassert (0 <= fd && fd < FD_SETSIZE);
+	for (; all_lim <= fd; all_lim++)
+	  {
+	    FD_CLR (all_lim, &all_rfds);
+	    FD_CLR (all_lim, &all_wfds);
+	  }
+	if (gfds[i].events & G_IO_IN)
+	  {
+	    eassert (! (rfds && fd < fds_lim && FD_ISSET (fd, rfds)));
+	    FD_SET (fd, &all_rfds);
+	  }
+	if (gfds[i].events & G_IO_OUT)
+	  {
+	    eassert (! (wfds && fd < fds_lim && FD_ISSET (fd, wfds)));
+	    FD_SET (fd, &all_wfds);
+	  }
+	if (gfds[i].events & G_IO_PRI)
+	  FD_SET (fd, &all_efds);
+      }
 
   SAFE_FREE ();
 
@@ -95,34 +105,28 @@
 	tmop = &tmo;
     }
 
-  fds_lim = max_fds + 1;
-  nfds = pselect (fds_lim, &all_rfds, have_wfds ? &all_wfds : NULL,
-		  efds, tmop, sigmask);
+  nfds = pselect (all_lim, &all_rfds, &all_wfds, &all_efds, tmop, sigmask);
 
   if (nfds < 0)
     retval = nfds;
-  else if (nfds > 0)
+  else
     {
       for (i = 0; i < fds_lim; ++i)
         {
-          if (FD_ISSET (i, &all_rfds))
-            {
-              if (rfds && FD_ISSET (i, rfds)) ++retval;
-              else ++our_fds;
-            }
-          else if (rfds)
-            FD_CLR (i, rfds);
-
-          if (have_wfds && FD_ISSET (i, &all_wfds))
-            {
-              if (wfds && FD_ISSET (i, wfds)) ++retval;
-              else ++our_fds;
-            }
-          else if (wfds)
-            FD_CLR (i, wfds);
-
-          if (efds && FD_ISSET (i, efds))
-            ++retval;
+	  if (rfds && FD_ISSET (i, rfds))
+	    {
+	      if (FD_ISSET (i, &all_rfds))
+		retval++;
+	      else
+		FD_CLR (i, rfds);
+	    }
+	  if (wfds && FD_ISSET (i, wfds))
+	    {
+	      if (FD_ISSET (i, &all_wfds))
+		retval++;
+	      else
+		FD_CLR (i, wfds);
+	    }
         }
     }
 
@@ -142,7 +146,7 @@
     }
 
   /* To not have to recalculate timeout, return like this.  */
-  if ((our_fds > 0 || (nfds == 0 && tmop == &tmo)) && (retval == 0))
+  if (retval == 0 && (0 < nfds || tmop == &tmo))
     {
       retval = -1;
       errno = EINTR;