Small bug in zsh 2.6beta9

Small bug in zsh 2.6beta9

[Heiko Schroeder]

Hi!

I found a small bug in zsh 2.6beta9.

In the file exec.c, line 493, the line

    if (ornext ^ ret) {

should read

    if (ornext ^ (ret!=0)) {

to get the documented behaviour of && and || in regard to being true
for values not equal to zero.

CU
   Heiko


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Re: Small bug in zsh 2.6beta9

[P.Stephenson]

heiko@pool.informatik.rwth-aachen.de wrote:
> In the file exec.c, line 493, the line
> 
>     if (ornext ^ ret) {
> 
> should read
> 
>     if (ornext ^ (ret!=0)) {

You're quite right --- this is my fault again.  Here's an actual patch
for that.

*** Src/exec.c.ret	Mon Jun  5 10:16:14 1995
--- Src/exec.c	Mon Jun  5 10:34:30 1995
***************
*** 506,512 ****
  	     */
  	    ornext = (slist->type == ORNEXT);
  
! 	    if (ornext ^ ret) {
  		/*
  		 * If either (1) it's an or, and the return code
  		 * was zero, or (2) it's an and, and the return
--- 506,512 ----
  	     */
  	    ornext = (slist->type == ORNEXT);
  
! 	    if (ornext ^ (ret != 0)) {
  		/*
  		 * If either (1) it's an or, and the return code
  		 * was zero, or (2) it's an and, and the return

-- 
Peter Stephenson <P.Stephenson@swansea.ac.uk>  Tel: +44 1792 205678 extn. 4461
WWW:  http://python.swan.ac.uk/~pypeters/      Fax: +44 1792 295324
Department of Physics, University of Wales, Swansea,
Singleton Park, Swansea, SA2 8PP, U.K.

Re: Small bug in zsh 2.6beta9

[Zvi Har'El]

Peter,

YOU were right all the time. The two lines of code are identical. Perhaps
the idiom of checking if(a) rather then if(a!=0) is not clear to people
who are not seasoned C programmers, but personally I prefer your original code.


On Mon Jun  5 12:37:34 1995, P.Stephenson@swansea.ac.uk wrote about ``Re: Small bug in zsh 2.6beta9'':
> 
> heiko@pool.informatik.rwth-aachen.de wrote:
> > In the file exec.c, line 493, the line
> > 
> >     if (ornext ^ ret) {
> > 
> > should read
> > 
> >     if (ornext ^ (ret!=0)) {
> 
> You're quite right --- this is my fault again.  Here's an actual patch
> for that.
> 
> *** Src/exec.c.ret	Mon Jun  5 10:16:14 1995
> --- Src/exec.c	Mon Jun  5 10:34:30 1995
> ***************
> *** 506,512 ****
>   	     */
>   	    ornext = (slist->type == ORNEXT);
>   
> ! 	    if (ornext ^ ret) {
>   		/*
>   		 * If either (1) it's an or, and the return code
>   		 * was zero, or (2) it's an and, and the return
> --- 506,512 ----
>   	     */
>   	    ornext = (slist->type == ORNEXT);
>   
> ! 	    if (ornext ^ (ret != 0)) {
>   		/*
>   		 * If either (1) it's an or, and the return code
>   		 * was zero, or (2) it's an and, and the return
> 
> -- 
> Peter Stephenson <P.Stephenson@swansea.ac.uk>  Tel: +44 1792 205678 extn. 4461
> WWW:  http://python.swan.ac.uk/~pypeters/      Fax: +44 1792 295324
> Department of Physics, University of Wales, Swansea,
> Singleton Park, Swansea, SA2 8PP, U.K.
> 
> 
> 


-- 
Dr. Zvi Har'El <rl@math.technion.ac.il>              Department of Mathematics
+972-4-294094(Phone)                 Technion - Israel Institute of Technology
+972-4-324654(FAX)     http://gauss.technion.ac.il/~rl     Haifa 32000, ISRAEL
``If you can't say somethin' nice, don't say nothin' at all.''--Thumper (1942)

Re: Small bug in zsh 2.6beta9

[Bas V. de Bakker]

Zvi Har'El <rl@leeor.technion.ac.il> writes:

>> >     if (ornext ^ ret) {
>> > 
>> > should read
>> > 
>> >     if (ornext ^ (ret!=0)) {

> YOU were right all the time. The two lines of code are
> identical. Perhaps the idiom of checking if(a) rather then if(a!=0)
> is not clear to people who are not seasoned C programmers, but
> personally I prefer your original code.

I haven't really followed the discussion, but although "if (a)" and
"if (a!=0)" are equivalent, the two lines above certainly aren't.  If
ornext == 1 and ret == 2 then

ornext ^ ret == 3

but

ornext ^ (ret != 0) == 0

Bas.