Re: perl native musl, ldd

[Rich Felker <dalias@libc.org>]

On Thu, Apr 02, 2015 at 04:40:22PM -0400, Jean-Marc Pigeon wrote:
> On 04/02/2015 02:48 PM, u-wsnj@aetey.se wrote:
> > On Thu, Apr 02, 2015 at 02:17:36PM -0400, Jean-Marc Pigeon wrote:
> >>>> bash-4.3# ldd SysV.so
> >>>> 	ldd (0x7f5d60dd2000)
> >>>> 	libc.so => ldd (0x7f5d60dd2000)
> >>>> Error relocating SysV.so: Perl_croak: symbol not found
> >>>> Error relocating SysV.so: Perl_sv_setiv: symbol not found
> >>>> Error relocating SysV.so: Perl_sv_2pv_flags: symbol not found
> >>>> Error relocating SysV.so: Perl_av_store: symbol not found
> >>>> etc.
> > 
> >> I am using a packager using ldd to establish
> >> dependencies list.
> > 
> > I would not say reporting the symbols is a bug, rather that the packager
> > is kind of relying on UB. Is there a specification of how a program called
> > "ldd" shall format its output and which data shall be present?
> > 
> > Rune
> > 
> Packager Relying on ldd UB, sure!.

I think calling this "UB" is a misappropriation of an unrelated term
just to criticize what you're doing. You are relying on a complex
utility that might have OS/libc-specific behavior that doesn't match
your expectations, or that might not even exist on some systems, but
that's not automatically a horrible thing as long as you know your
system(s).

> Using ldd was the best way I found to list one package all
> dependencies (looking at ELF file type ans searching for
> required external components).
> If you have a better way (more standard) to propose not using
> ldd that will be a good thing. idea?

Using readelf (or your own ELF parsing) and looking for the DT_NEEDED
entries would perhaps be a cleaner approach. It would only list direct
dependencies rather than recursive ones and it would not depend on
running target code (i.e. it would work equally well with
cross-compiled packages).

Of course this does not cover all dependencies (non-library things)
but it at least automates a large part of the dependency tracking
process.

Rich