Re: FreeBSD compatability feature request

[Peter Stephenson <pws@xxxxxxx>]

Vincent Stemen wrote:
> Here is the FreeBSD manual entry:
> 
>   -T trapsasync
>         When waiting for a child, execute traps immediately.  If this
>         option is not set, traps are executed after the child exits,
>         as specified in IEEE Std 1003.2 (``POSIX.2'') This nonstandard
>         option is useful for putting guarding shells around children
>         that block signals.  The surrounding shell may kill the child
>         or it may just return control to the tty and leave the child
>         alone, like this:
> 
>            sh -T -c "trap 'exit 1' 2 ; some-blocking-program"

Good(ish) news...

Just tried this out, and it looks like the `trapsasync' behaviour
is the standard (and only) one in zsh.  Hence it doesn't conform to
POSIX (which isn't likely to be an earth-shattering revelation to zsh
regulars).

This means that almost everything we need for both behaviours is already
there.  It remains to add the option TRAPS_ASYNC, turned on by default
in non-Bourne mode for compatibility, and make sure we can still handle
SIGCHLD when the option is unset.

Someone already had the foresight to handle sh options separately, so -T
does the right thing in sh or ksh emulation and the example you gave
should now work as expected.

Further follow-ups should probably go to zsh-workers.

Index: Doc/Zsh/options.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/options.yo,v
retrieving revision 1.30
diff -u -r1.30 options.yo
--- Doc/Zsh/options.yo	6 Mar 2004 00:23:03 -0000	1.30
+++ Doc/Zsh/options.yo	19 Apr 2004 11:13:25 -0000
@@ -1189,6 +1189,14 @@
 Remove any right prompt from display when accepting a command
 line.  This may be useful with terminals with other cut/paste methods.
 )
+pindex(TRAPS_ASYNC)
+cindex(traps, asynchronous)
+item(tt(TRAPS_ASYNC) <C> <Z>)(
+While waiting for a program to exit, run traps immediately.  Otherwise
+the trap is run after the program has exited.  Note this does not affect
+the point at which traps are run for any case other than when the shell is
+waiting for a child process.
+)
 pindex(TYPESET_SILENT)
 item(tt(TYPESET_SILENT))(
 If this is unset, executing any of the `tt(typeset)' family of
@@ -1366,6 +1374,7 @@
 subsect(sh/ksh emulation set)
 startsitem()
 sitem(tt(-C))(em(NO_)CLOBBER)
+sitem(tt(-T))(TRAPS_ASYNC)
 sitem(tt(-X))(MARK_DIRS)
 sitem(tt(-a))(ALL_EXPORT)
 sitem(tt(-b))(NOTIFY)
Index: Src/jobs.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/jobs.c,v
retrieving revision 1.25
diff -u -r1.25 jobs.c
--- Src/jobs.c	17 Feb 2004 10:41:37 -0000	1.25
+++ Src/jobs.c	19 Apr 2004 11:13:25 -0000
@@ -994,7 +994,11 @@
     int q = queue_signal_level();
     Job jn = jobtab + job;
 
-    dont_queue_signals();
+    queue_not_sigchld++;
+    if (isset(TRAPSASYNC))
+	dont_queue_signals();
+    else
+	queue_signals();
     child_block();		 /* unblocked during child_suspend() */
     if (jn->procs || jn->auxprocs) { /* if any forks were done         */
 	jn->stat |= STAT_LOCKED;
@@ -1026,6 +1030,9 @@
     }
     child_unblock();
     restore_queue_signals(q);
+    if (!queueing_enabled)
+	run_queued_signals();
+    queue_not_sigchld--;
 }
 
 /* wait for running job to finish */
Index: Src/options.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/options.c,v
retrieving revision 1.17
diff -u -r1.17 options.c
--- Src/options.c	6 Mar 2004 00:23:03 -0000	1.17
+++ Src/options.c	19 Apr 2004 11:13:25 -0000
@@ -203,6 +203,7 @@
 {NULL, "singlelinezle",	      OPT_KSH,			 SINGLELINEZLE},
 {NULL, "sunkeyboardhack",     0,			 SUNKEYBOARDHACK},
 {NULL, "transientrprompt",    0,			 TRANSIENTRPROMPT},
+{NULL, "trapsasync",	      OPT_EMULATE|OPT_NONBOURNE, TRAPSASYNC},
 {NULL, "typesetsilent",	      OPT_EMULATE|OPT_BOURNE,	 TYPESETSILENT},
 {NULL, "unset",		      OPT_EMULATE|OPT_BSHELL,	 UNSET},
 {NULL, "verbose",	      0,			 VERBOSE},
@@ -346,7 +347,7 @@
     /* Q */  0,
     /* R */  0,
     /* S */  0,
-    /* T */  0,
+    /* T */  TRAPSASYNC,
     /* U */  0,
     /* V */  0,
     /* W */  0,
Index: Src/signals.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/signals.c,v
retrieving revision 1.25
diff -u -r1.25 signals.c
--- Src/signals.c	25 Mar 2004 10:07:15 -0000	1.25
+++ Src/signals.c	19 Apr 2004 11:13:25 -0000
@@ -49,7 +49,7 @@
 /* Variables used by signal queueing */
 
 /**/
-mod_export int queueing_enabled, queue_front, queue_rear;
+mod_export int queueing_enabled, queue_front, queue_rear, queue_not_sigchld;
 /**/
 mod_export int signal_queue[MAX_QUEUE_SIZE];
 /**/
@@ -425,7 +425,8 @@
     }
 #endif
 
-    if (queueing_enabled) {           /* Are we queueing signals now?      */
+    /* Are we queueing signals now?      */
+    if (queueing_enabled && (sig != SIGCHLD || !queue_not_sigchld)) {
         int temp_rear = ++queue_rear % MAX_QUEUE_SIZE;
 
 	DPUTS(temp_rear == queue_front, "BUG: signal queue full");
Index: Src/zsh.h
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/zsh.h,v
retrieving revision 1.54
diff -u -r1.54 zsh.h
--- Src/zsh.h	11 Mar 2004 14:25:12 -0000	1.54
+++ Src/zsh.h	19 Apr 2004 11:13:25 -0000
@@ -1523,6 +1523,7 @@
     SINGLELINEZLE,
     SUNKEYBOARDHACK,
     TRANSIENTRPROMPT,
+    TRAPSASYNC,
     TYPESETSILENT,
     UNSET,
     VERBOSE,

-- 
Peter Stephenson <pws@xxxxxxx>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 692070


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