bug: ZERR traps and functions.

bug: ZERR traps and functions.

[Gene Carter]

[-- Attachment #1: Type: text/plain, Size: 816 bytes --]

Greetings,

I believe I've found a bug in how ZSH handles functions and error trapping.

with zsh 4.3.2 on AIX 4.3.3...

If you set error trapping and a function returns non-zero, the shell exits,
but the code specified in the trap doesn't get executed.

This appears to be because of line 866 in exec.c, where the execution of
code depends on retflag being zero. Going in and taking out that condition
allows the code to work, but I don't have a concept for how many other
things that breaks.

Example of the bug:

########################
function a
{
    return 1
}

trap "print err" ZERR
set -e

print "###############\npre a"
a
print "post a\n###############"
##########################

Output:
17:33: [rfgadm@isriscwc {8}] /rfgadm/zsh 2
###############
pre a
17:33: [rfgadm@isriscwc {9}]

Thanks,
Gene Carter

[-- Attachment #2: Type: text/html, Size: 984 bytes --]

Re: bug: ZERR traps and functions.

[Peter Stephenson]

On Wed, 10 Jan 2007 17:41:13 -0500
"Gene Carter" <gananda@gmail.com> wrote:
> I believe I've found a bug in how ZSH handles functions and error trapping.
> 
> with zsh 4.3.2 on AIX 4.3.3...
> 
> If you set error trapping and a function returns non-zero, the shell exits,
> but the code specified in the trap doesn't get executed.

Right, this occurs with an explicit "return" returning non-zero from a
function nested within the code where ERR_EXIT is set, not with an
instruction that merely causes an implicit return because of its exit
status.

Then I noticed that without ERR_EXIT set the rules for returning the
status from a return within the trap weren't being obeyed, either.
Specifically, the special case of a non-zero return status from TRAPZERR
should trigger a return from an enclosing function with the same status,
but while it did trigger a return, the status was lost.  (See
description of TRAPNAL in "Special Functions" in zshmisc.)  The other
cases (trap '...' ZERR, or returning 0 from TRAPZERR) worked OK.

I hate traps.

Index: Src/signals.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/signals.c,v
retrieving revision 1.42
diff -u -r1.42 signals.c
--- Src/signals.c	19 Dec 2006 10:35:55 -0000	1.42
+++ Src/signals.c	12 Jan 2007 22:56:34 -0000
@@ -1071,6 +1071,7 @@
     char *name, num[4];
     int trapret = 0;
     int obreaks = breaks;
+    int oretflag = retflag;
     int isfunc;
     int traperr;
 
@@ -1109,7 +1110,7 @@
 
     lexsave();
     execsave();
-    breaks = 0;
+    breaks = retflag = 0;
     runhookdef(BEFORETRAPHOOK, NULL);
     if (*sigtr & ZSIG_FUNC) {
 	int osc = sfcontext;
@@ -1176,15 +1177,20 @@
 	if (isfunc) {
 	    breaks = loops;
 	    errflag = 1;
+	    lastval = trapret;
 	} else {
 	    lastval = trapret-1;
 	}
+	/* return triggered */
+	retflag = 1;
     } else {
 	if (traperr && emulation != EMULATE_SH)
 	    lastval = 1;
 	if (try_tryflag)
 	    errflag = traperr;
 	breaks += obreaks;
+	/* return not triggered: restore old flag */
+	retflag = oretflag;
 	if (breaks > loops)
 	    breaks = loops;
     }
Index: Test/C03traps.ztst
===================================================================
RCS file: /cvsroot/zsh/zsh/Test/C03traps.ztst,v
retrieving revision 1.9
diff -u -r1.9 C03traps.ztst
--- Test/C03traps.ztst	3 Mar 2006 22:09:58 -0000	1.9
+++ Test/C03traps.ztst	12 Jan 2007 22:56:34 -0000
@@ -287,6 +287,69 @@
 >child exiting
 >wait #2 finished, gotsig=0, status=33
 
+  fn1() {
+    setopt errexit
+    trap 'echo error1' ZERR
+    false
+    print Shouldn\'t get here 1a
+  }
+  fn2() {
+    setopt errexit
+    trap 'echo error2' ZERR
+    return 1
+    print Shouldn\'t get here 2a
+  }
+  fn3() {
+    setopt errexit
+    TRAPZERR() { echo error3; }
+    false
+    print Shouldn\'t get here 3a
+  }
+  fn4() {
+    setopt errexit
+    TRAPZERR() { echo error4; }
+    return 1
+    print Shouldn\'t get here 4a
+  }
+  (fn1; print Shouldn\'t get here 1b)
+  (fn2; print Shouldn\'t get here 2b)
+  (fn3; print Shouldn\'t get here 3b)
+  (fn4; print Shouldn\'t get here 4b)
+1: Combination of ERR_EXIT and ZERR trap
+>error1
+>error2
+>error3
+>error4
+
+   fn1() { TRAPZERR() { print trap; return 42; }; false; print Broken; }
+   (fn1)
+   print Working $?
+0: Force return of containing function from TRAPZERR.
+>trap
+>Working 42
+
+   fn2() { trap 'print trap; return 42' ZERR; false; print Broken }
+   (fn2)
+   print Working $?
+0: Return with non-zero status triggered from within trap '...' ZERR.
+>trap
+>Working 42
+
+   fn3() { TRAPZERR() { print trap; return 0; }; false; print OK this time; }
+   (fn3)
+   print Working $?
+0: Normal return from TRAPZERR.
+>trap
+>OK this time
+>Working 0
+
+   fn4() { trap 'print trap; return 0' ZERR; false; print Broken; }
+   (fn4)
+   print Working $?
+0: Return with zero status triggered from within trap '...' ZERR.
+>trap
+>Working 0
+
 %clean
 
   rm -f TRAPEXIT

-- 
Peter Stephenson <p.w.stephenson@ntlworld.com>
Web page now at http://homepage.ntlworld.com/p.w.stephenson/