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Re: pkg/51152 (pkg_alternatives via shebang won't continue and will use previous shell)
The following reply was made to PR pkg/51152; it has been noted by GNATS.
From: Julio Merino <julio%meroh.net@localhost>
To: David Holland <dholland-pbugs%netbsd.org@localhost>
Subject: Re: pkg/51152 (pkg_alternatives via shebang won't continue and will
use previous shell)
Date: Mon, 4 Jul 2016 23:14:26 -0400
On Mon, Jul 4, 2016 at 9:38 PM, David Holland <dholland-pbugs%netbsd.org@localhost> wrote:
> On Sun, Jul 03, 2016 at 02:41:13AM +0000, jmmv%NetBSD.org@localhost wrote:
> > Yup... This was years ago, so if I had to guess as to why this problem
> > exists, it's probably because I did not know that shell scripts could
> > not act as full-blown interpreters back then.
> > Rewritting the wrapper in C is a good answer and should be relatively
> > straightforward; it's a pretty rudimentary program.
> Unfortunately it looks like it needs to be recompiled on the fly
> outside the pkgsrc compilation environment... that or the whole thing
> needs to be restructured so there can be one binary wrapper compiled
> in advance and a way to look up what's currently baked into the script
> file at creation time.
> That or do some kind of binary patching horror.
From a second look... I see these three classes of "settings" in wrapper.sh:
* ID, ROOT_USER: These are static variables defined at "configure
time" so they can just be baked into the binary.
* WRAPPER: The name of the actual wrapper. Could possibly just be
derived from "basename of argv" (?), in which case the wrapper
binary would suit any alternative.
* DB_FILE, CONFFILE: Paths to files. These are built from a static
setting determined at "configure time" (e.g. path to the system-wide
configuration directory, or a path to a home directory), and a dynamic
piece. The latter seems to be just the value of WRAPPER. If that's
correct, then the same as in the previous applies.
In other words: if the wrapper code is changed to rely on the contents
of argv, it should be possible to reuse the exact same binary for
Julio Merino -- http://julio.meroh.net/
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