Fix for EXIT traps

[Peter Stephenson <pws@xxxxxx>]

A trap for SIGEXIT is supposed to be sprung in the calling
environment; this is its primary use for functions.  To make this
consistent, that means that the trap for SIGEXIT should itself reflect
the caller when the trap is sprung.  For example,

% fn() { trap 'trap "Exit trap for calling shell" EXIT' EXIT }
% fn

is the way to set an EXIT trap in the parent shell of a function.
Currently zsh doesn't handle this correctly.  

This patch fixes this.  In fact, it's only been worth handling
correctly seen Zoltan fixed traps in the form given above; before
that, all traps ran as a separate function and these subtleties were
lost (and debugging was a lot more difficult).  Much of the patch is a
minor rewrite to dotrap() which allows the code to be called for
signal functions which are not currently installed.

I have also been careful to make code like:

% trap 'echo The original exit trap' EXIT
% fn() { trap 'trap >storeoldtraps' EXIT; }
% fn
% cat storeoldtraps
trap -- 'echo The original exit trap' EXIT

work too.  (Unfortunately, `storeoldtraps=$(trap)' doesn't work,
although it does in ksh.  Whether this is the right effect in a
subshell is not clear.)

If anyone can think of a workaround for setting an EXIT trap for a
shell from within a function, I'd be interested to hear it anyway.  I
can only think of some rather brutal asynchronous possibilities.


*** Src/exec.c.se	Wed Feb  5 15:53:02 1997
--- Src/exec.c	Tue Feb 11 13:53:00 1997
***************
*** 2515,2524 ****
  {
      Param pm;
      char **tab, **x, *oargv0 = NULL;
!     int xexittr, oldzoptind, oldlastval;
      LinkList olist;
      char *s, *ou;
!     void *xexitfn;
      char saveopts[OPT_SIZE];
      int obreaks = breaks;
  
--- 2515,2524 ----
  {
      Param pm;
      char **tab, **x, *oargv0 = NULL;
!     int xexittr, newexittr, oldzoptind, oldlastval;
      LinkList olist;
      char *s, *ou;
!     void *xexitfn, *newexitfn;
      char saveopts[OPT_SIZE];
      int obreaks = breaks;
  
***************
*** 2610,2620 ****
  	    opts[LOCALOPTIONS] = saveopts[LOCALOPTIONS];
  	}
  
! 	/* Did the shell function define a trap on SIGEXIT? */
! 	if (sigfuncs[SIGEXIT]) {
! 	    dotrap(SIGEXIT);
! 	    unsettrap(SIGEXIT);
! 	}
  
  	sigtrapped[SIGEXIT] = xexittr;
  	if (xexittr & ZSIG_FUNC) {
--- 2610,2624 ----
  	    opts[LOCALOPTIONS] = saveopts[LOCALOPTIONS];
  	}
  
! 	/*
! 	 * The trap '...' EXIT runs in the environment of the caller,
! 	 * so remember it here but run it after resetting the
! 	 * traps for the parent.
! 	 */
! 	newexittr = sigtrapped[SIGEXIT];
! 	newexitfn = sigfuncs[SIGEXIT];
! 	if (newexittr & ZSIG_FUNC)
! 	    shfunctab->removenode(shfunctab, "TRAPEXIT");
  
  	sigtrapped[SIGEXIT] = xexittr;
  	if (xexittr & ZSIG_FUNC) {
***************
*** 2622,2627 ****
--- 2626,2637 ----
  	    sigfuncs[SIGEXIT] = ((Shfunc) xexitfn)->funcdef;
  	} else
  	    sigfuncs[SIGEXIT] = (List) xexitfn;
+ 
+ 	if (newexitfn) {
+ 	    dotrapargs(SIGEXIT, &newexittr, newexitfn);
+ 	    freestruct(newexitfn);
+ 	}
+ 
  	if (trapreturn < -1)
  	    trapreturn++;
  	if (noreturnval)
*** Src/signals.c.se	Tue Feb 11 13:27:46 1997
--- Src/signals.c	Tue Feb 11 13:49:50 1997
***************
*** 655,665 ****
      }
  }
  
! /* Execute a trap function for a given signal */
  
  /**/
  void
! dotrap(int sig)
  {
      LinkList args;
      char *name, num[4];
--- 655,667 ----
      }
  }
  
! /* Execute a trap function for a given signal, possibly
!  * with non-standard sigtrapped & sigfuncs values
!  */
  
  /**/
  void
! dotrapargs(int sig, int *sigtr, void *sigfn)
  {
      LinkList args;
      char *name, num[4];
***************
*** 674,688 ****
       * intact without working too hard.  Special cases (e.g. calling  *
       * a trap for SIGINT after the error flag was set) are handled    *
       * by the calling code.  (PWS 1995/06/08).			      */
!     if ((sigtrapped[sig] & ZSIG_IGNORED) || !sigfuncs[sig] || errflag)
          return;
  
!     sigtrapped[sig] |= ZSIG_IGNORED;
  
      lexsave();
      execsave();
      breaks = 0;
!     if (sigtrapped[sig] & ZSIG_FUNC) {
  	PERMALLOC {
  	    args = newlinklist();
  	    name = (char *) zalloc(5 + strlen(sigs[sig]));
--- 676,690 ----
       * intact without working too hard.  Special cases (e.g. calling  *
       * a trap for SIGINT after the error flag was set) are handled    *
       * by the calling code.  (PWS 1995/06/08).			      */
!     if ((*sigtr & ZSIG_IGNORED) || !sigfn || errflag)
          return;
  
!     *sigtr |= ZSIG_IGNORED;
  
      lexsave();
      execsave();
      breaks = 0;
!     if (*sigtr & ZSIG_FUNC) {
  	PERMALLOC {
  	    args = newlinklist();
  	    name = (char *) zalloc(5 + strlen(sigs[sig]));
***************
*** 692,702 ****
  	    addlinknode(args, num);
  	} LASTALLOC;
  	trapreturn = -1;
! 	doshfunc(sigfuncs[sig], args, 0, 1);
  	freelinklist(args, (FreeFunc) NULL);
  	zsfree(name);
      } else HEAPALLOC {
! 	execlist(dupstruct(sigfuncs[sig]), 1, 0);
      } LASTALLOC;
      if (trapreturn > 0)
  	trapret = trapreturn;
--- 694,704 ----
  	    addlinknode(args, num);
  	} LASTALLOC;
  	trapreturn = -1;
! 	doshfunc(sigfn, args, 0, 1);
  	freelinklist(args, (FreeFunc) NULL);
  	zsfree(name);
      } else HEAPALLOC {
! 	execlist(dupstruct(sigfn), 1, 0);
      } LASTALLOC;
      if (trapreturn > 0)
  	trapret = trapreturn;
***************
*** 714,719 ****
  	    breaks = loops;
      }
  
!     if (sigtrapped[sig] != ZSIG_IGNORED)
! 	sigtrapped[sig] &= ~ZSIG_IGNORED;
  }
--- 716,730 ----
  	    breaks = loops;
      }
  
!     if (*sigtr != ZSIG_IGNORED)
! 	*sigtr &= ~ZSIG_IGNORED;
! }
! 
! /* Standard call to execute a trap for a given signal */
! 
! /**/
! void
! dotrap(int sig)
! {
!     dotrapargs(sig, sigtrapped+sig, sigfuncs[sig]);
  }

-- 
Peter Stephenson <pws@xxxxxx>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77413
Deutsches Elektronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, 15735 Zeuthen, Germany.