[Nix-dev] patchelf - why rpath, not runpath?

[Lluís Batlle]

Hello,

reading from ld.so, I see the order of checking directories for
libraries goes as follows:
1 - rpath
2 - $LD_LIBRARY_PATH
3 - runpath
4 - ld.so.cache
5 - default ld.so directories (where glibc has been installed)

Is there any rationale behind the decision choosing rpath? Wouldn't
the runpath allow easier library substitution with $LD_LIBRARY_PATH,
and this would be a benefit?

Maybe the rpath and runpath have clear different "usual applications"
in a gnu/elf system, I don't know.

Regards,
Lluís.