app/main.c libgimp/gimpsignal.c [Documentation only] Patches arising from

2000-04-30 Garry R. Osgood <gosgood@idt.net>
* app/main.c
* libgimp/gimpsignal.c [Documentation only]
Patches arising from Tim Mooney to fix #2742
which should (hopefully) die at this point.
removes on_sig_chld() from app/main() which
offers no meaningful functionality in light
of SA_NOCHLDSTOP.

ChangeLog

@@ -1,3 +1,22 @@
+2000-04-30 Garry R. Osgood <gosgood@idt.net>
+	* app/main.c
+	* libgimp/gimpsignal.c [Documentation only]
+
+	Based on a patch and testing furnished by Tim Mooney
+ 	<mooney@dogbert.cc.ndsu.nodak.edu> Retiring app/main.c
+ 	on_sig_chld(); at best this function is schizoid: On the left hand it
+ 	employs a facility for processes that have nothing better to do
+ 	than sleep until children die. (waitpid()) But it employs this
+ 	policy on the right hand, in a SIGCLD handler, a facility for
+ 	processes that have better things to do than sleep until children
+ 	die (!). And - at worse - it appeared to be contributing to the
+ 	ongoing #2742 saga. Mr. Mooney and I concur that for now asking
+ 	POSIX OS's not to generate SIGCLD at all is better than asking
+ 	mentally divided functions to handle them. Eventually we will need
+ 	SIGCLD handlers to implement runtime plug-in management (Mitch:
+ 	"gimp_nanny()") When we come to that fork in the road (;)), we
+ 	will need to work carefully so as not to re-introduce #2742.
+
 2000-04-30  Sven Neumann  <sven@gimp.org>
 
 	* app/gimage_cmds.c: reverted Asbjorns change (changing this file

app/main.c

@@ -55,7 +55,6 @@
 #include <windows.h>
 #else
 static void       on_signal       (gint);
-static void       on_sig_child    (gint);
 #endif
 
 static void       init            (void);
@@ -345,10 +344,16 @@ main (int    argc,
   gimp_signal_syscallrestart (SIGTERM, on_signal);
   gimp_signal_syscallrestart (SIGFPE,  on_signal);
 
-  /* Handle child exits */
+#ifndef __EMX__ /* OS/2 may not support SA_NOCLDSTOP -GRO */
 
-  gimp_signal_syscallrestart (SIGCHLD, on_sig_child);
+  /* Disable child exit notification.  This doesn't just block */
+  /* receipt of SIGCHLD, it in fact completely disables the    */
+  /* generation of the signal by the OS.  This behavior is     */
+  /* mandated by POSIX.1.                                      */
 
+  gimp_signal_private (SIGCHLD, NULL, SA_NOCLDSTOP);
+
+#endif
 #endif
 
   g_log_set_handler (NULL, G_LOG_LEVEL_ERROR | G_LOG_FLAG_FATAL,
@@ -464,20 +469,4 @@ on_signal (gint sig_num)
     }
 }
 
-/* gimp core signal handler for death-of-child signals */
-
-static void
-on_sig_child (gint sig_num)
-{
-  gint pid;
-  gint status;
-
-  while (1)
-    {
-      pid = waitpid (WAIT_ANY, &status, WNOHANG);
-      if (pid <= 0)
-	break;
-    }
-}
-
 #endif /* !G_OS_WIN32 */

libgimp/gimpsignal.c

@@ -53,9 +53,16 @@ gimp_signal_private (gint signum, void (*gimp_sighandler)(int), gint sa_flags)
   struct sigaction sa;
   struct sigaction osa;
 
-  /* this field is a union of sa_sighandler.sa_sighandler1 and */
+  /* The sa_handler (mandated by POSIX.1) and sa_sigaction (a      */
-  /* sa_sigaction1 - don't set both at once...                 */
+  /* common extension) are often implemented by the OS as members  */
+  /* of a union.  This means you CAN NOT set both, you set one or  */
+  /* the other.  Caveat programmer!                                */
 
+  /* Passing gimp_signal_private a gimp_sighandler of NULL is not  */
+  /* an error, and generally results in the action for that signal */
+  /* being set to SIG_DFL (default behavior).  Many OSes define    */
+  /* SIG_DFL as (void (*)()0, so setting sa_handler to NULL is     */
+  /* the same thing as passing SIG_DFL to it.                      */
   sa.sa_handler   = gimp_sighandler;
 
   /* Mask all signals while handler runs to avoid re-entrancy

libgimpbase/gimpsignal.c

@@ -53,9 +53,16 @@ gimp_signal_private (gint signum, void (*gimp_sighandler)(int), gint sa_flags)
   struct sigaction sa;
   struct sigaction osa;
 
-  /* this field is a union of sa_sighandler.sa_sighandler1 and */
+  /* The sa_handler (mandated by POSIX.1) and sa_sigaction (a      */
-  /* sa_sigaction1 - don't set both at once...                 */
+  /* common extension) are often implemented by the OS as members  */
+  /* of a union.  This means you CAN NOT set both, you set one or  */
+  /* the other.  Caveat programmer!                                */
 
+  /* Passing gimp_signal_private a gimp_sighandler of NULL is not  */
+  /* an error, and generally results in the action for that signal */
+  /* being set to SIG_DFL (default behavior).  Many OSes define    */
+  /* SIG_DFL as (void (*)()0, so setting sa_handler to NULL is     */
+  /* the same thing as passing SIG_DFL to it.                      */
   sa.sa_handler   = gimp_sighandler;
 
   /* Mask all signals while handler runs to avoid re-entrancy