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Message-ID: <20170517190705.GM6320@example.net>
Date: Wed, 17 May 2017 21:07:05 +0200
From: u-uy74@...ey.se
To: musl@...ts.openwall.com
Subject: Re: Question about setting argv[0] when manually using
dynamic linker
On Wed, May 17, 2017 at 12:24:28PM -0400, Rich Felker wrote:
> > >>> On Tue, May 16, 2017 at 08:38:56PM -0400, John Regan wrote:
> > >>> > Hi there - I was wondering if it's possible to somehow set argv[0] when
> > >>> > calling the dynamic linker to load a program.
> > >>> Set argv[0] to whatever you need when you exec*() the dynamic loader,
> > >>> which is straightforward with a binary wrapper (not with a shell).
> > >>>
> > >>> A binary wrapper also adds less overhead then going through a shell.
> > >>> Rune
> a completely reasonable and recommended way for deploying dynamic
> linked apps in a self-contained way that doesn't depend on musl libc
> on the host. Unfortunately there's no way to set argv[0] like you want
We do deploy dynamic linked apps without any dependencies on the libraries
on the host. It works just fine with musl-as-it-is, including the
questionably designed applications like busybox and gcc who
analyze argv[0].
> at this time. Perhaps adding an option like --argv0=foo would be
> appropriate.
What would be the justification for adding the supporting code (to every
instance of the dynamic loader)?
It looks like --argv0=foo is meant to overcome a specific limitation in
bourne shell, in a specific context where the task can be solved easily
and generally better without involving the bourne shell in the first hand.
I would like to see an example of a situation where a wrapper in C (or
any language allowing setting of argv[0]) is less appropriate?
If one really has a reason to express the wrapper in sh, a one-liner in
C and an extra exec from the shell (much cheaper than starting the
shell itself was) is sufficient to make it work.
Rune
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