bug#41037: documentation for application developers?

[Bruno Haible]

Hi Danny,

> > So, the consequence is that a Guix user cannot send an executable
> > to another Guix user and expect it to be runnable on the other machine.
> 
> Do you mean only one file, the executable?  That doesn't work well with any
> other distribution either.

Huh? I thought the purpose of the LSB specification is precisely that you
can take an executable from any modern Linux distro and run it on any other
modern Linux distro, with high success probability (not 100%, but close).

But when the different systems have the ld.so at different absolute locations,
it doesn't work.

> What guix can do is pack everything a package needs into a tarball
> (including dependencies too) and then put that on another machine.
> The command is "guix pack" (it can also create Docker containers
> and Singularity images--but regular tarballs work just fine).
> That does work reliably, and automatically does deduplication.

This is well documented in the manual. It's the other part, about
the "naked" executables, that I would have expected to find in the
documentation.

> > I wanted to have background information regarding ldconfig and shared
> > library caches, in order to investigate bug#41038
> > <https://lists.gnu.org/archive/html/bug-guix/2020-05/msg00036.html>.
> 
> ldconfig is not used in Guix.  Guix uses rpath in order to embed the
> entire path to each of the shared libraries that are used into the
> executable.
> ldconfig's name resolution is disabled.

This is valuable info! Can you just add this paragraph to the doc, please?

Bruno