Re: segfault with invalid shell script

[Christoph Anton Mitterer <calestyo@scientia.org>]

Hey Harald

On Mon, 2022-11-21 at 13:08 +0000, Harald van Dijk wrote:
> 
> This is intentionally accepted, like all non-standard 
> substitutions, during parsing, but is supposed to raise a
> substitution 
> error at runtime, so that scripts can do
> 
>    if shell_supports_subst; then
>      echo ${var//a/b}
>    else
>      echo $var | sed s/a/b/g
>    fi
> 
> Parsing this if statement requires parsing both sides of the branch, 
> even ${var//a/b} will never be evaluated.

Well, while I can understand the merit of this... it may also have some
drawbacks.


> Actually performing this substitution should result in an error:
> 
>    $ dash -c 'echo ${$//1/2}'
>    dash: 1: Bad substitution

It does here, too.

> What the intended behaviour here is though, is unclear. The
> substitution 
> containing ${...//...} is evaluated but the ${...//...} is skipped 
> because $restrict_path_list is unset.

In the original script, it may be set. I just shortened it.


> Fixing this so it produces "Bad substitution" should be easy, almost 
> trivial.

I, personally, would like that anyway better.

Conditionally choosing the variant of shell command language during
runtime seems quite fragile.
I'd rather see straight away, that I use something non-supported.



Is there some bugtracker for dash, so that it doesn't get forgotten?


Thanks,
Chris.