Re: GP handling of SIGINT (Linux)

[Jeroen Demeyer <J.Demeyer@UGent.be>]

Karim Belabas wrote:
> * Jeroen Demeyer [2005-04-17 21:35]:
>
> > Hello list,
> >
> > while hacking with GP and shell scripts under Linux, I noted the following:
> >
> > When using GP non-interactively (gp -f -q <commands.gp >output),
> > it only handles a SIGINT once.  The first SIGINT is caught and 
> > interrupts the current command (as usual), but any further SIGINTs do 
> > nothing.  I don't understand how come this behaviour is different from 
> > an interactive GP, where multiple SIGINTs can be cought.
> >
> > Is this a feature or a bug?
>
>
> It's a bug, which we've not been able to trace so far. See

Looking at the code, I have an idea on what's going wrong.  The problem 
seems to be with the use of longjmp().  This causes the function 
gp_sighandler() never to return, so the rest of the program is treated 
as being inside the signal handler.  By default a signal can never occur 
during a signal handler.

A very ugly hack around this is to change this default.  I have done 
this in attached patch.  I can only say it fixes my problem, but it 
could very well break things.  The behaviour is also likely to be 
OS-dependent.
? build.sh
? config/linux-i686-tmp19989
Index: src/language/es.c
===================================================================
RCS file: /home/cvs/pari/src/language/es.c,v
retrieving revision 1.168
diff -u -r1.168 es.c
--- src/language/es.c	6 Apr 2005 19:43:13 -0000	1.168
+++ src/language/es.c	18 Apr 2005 11:31:22 -0000
@@ -2741,7 +2741,15 @@
 #ifdef WINCE
   return SIG_IGN;
 #else
-  return signal(sig,f);
+  struct sigaction sa;
+  struct sigaction oldsa;
+  
+  sa.sa_handler = f;
+  sigemptyset(&sa.sa_mask);
+  sa.sa_flags = SA_NODEFER;
+  
+  if (sigaction(sig, &sa, &oldsa)) return NULL;
+  return oldsa.sa_handler;
 #endif
 }