Re: Using 'command -v' in a shellscript results in a coredump

[Michael Prokop <news@michael-prokop.at>]

* Bart Schaefer <schaefer@brasslantern.com> [20040819 09:15]:
> On Thu, 19 Aug 2004, Michael Prokop wrote:

> > #!/bin/sh
> > command -v blub > /dev/null 2>&1

> > Running it results in 'zsh: segmentation fault (core dumped)'.

> The following prevents the core dump without producing any errors from
> "make test", but I suspect there's something deeper that should be fixed
> instead.

> The crash happens whenever 'command -v' or 'command -V' is used with the 
> POSIXBUILTINS option set.

> The problem is that the code in execcmd() near line 1848 assigns 'hn' to
> point at the special 'commandbn' struct, but then 1952 is reached and
> tries (again) to find the builtin named "command" which fails.  Nothing
> picks up the error after that and a null 'hn' is eventually dereferenced
> by execbuiltin().

> Index: Src/exec.c
> ===================================================================
> RCS file: /cvsroot/zsh/zsh/Src/exec.c,v
> retrieving revision 1.69
> diff -u -r1.69 exec.c
> --- Src/exec.c	29 Jul 2004 15:09:51 -0000	1.69
> +++ Src/exec.c	19 Aug 2004 07:03:43 -0000
> @@ -1949,7 +1949,7 @@
>  		is_shfunc = 1;
>  		break;
>  	    }
> -	    if (!(hn = builtintab->getnode(builtintab, cmdarg))) {
> +	    if (!hn && !(hn = builtintab->getnode(builtintab, cmdarg))) {
>  		if (cflags & BINF_BUILTIN) {
>  		    zwarn("no such builtin: %s", cmdarg, 0);
>  		    lastval = 1;

Thanks, Bart. (I'm replying with latency because I wanted to wait
for any updates on this topic.)

In the current CVS sources from zsh (2004-10-07) this bug isn't
fixed AFAICS (refering to line 1978 of Src/exec.c).

Some post-install scripts on Debian systems use 'command -v'.
I'm using zsh as the '/bin/sh'-shell on my systems. When I'm
upgrading the systems I often have to do a 'rm /bin/sh; ln -s
/bin/bash /bin/sh' and point it back after process of upgrading to
avoid the mentioned core dumps.

Any chance to see this bug fixed in upcoming versions of zsh (with
above code)?

thx && regards,
(-: Michael