This page says about order for library search in ld.so
:
Unless loading object has RUNPATH: RPATH of the loading object, then the RPATH of its loader (unless it has a RUNPATH), ..., until the end of the chain, which is either the executable or an object loaded by dlopen Unless executable has RUNPATH: RPATH of the executable LD_LIBRARY_PATH RUNPATH of the loading object ld.so.cache default dirs
And then suggests:
When you ship binaries, either use RPATH and not RUNPATH or ensure LD_LIBRARY_PATH is set before they are run.
So, using RPATH
with RUNPATH
is bad because RUNPATH
kind-of cancels RPATH
so indirect dynamic loading doesn't work as expected? But why then RPATH
got deprecated in favor of RUNPATH
?
Can somebody explain the situation?
When you ship a binary, it's good to provide means for the users to accommodate the binary to the specifics of their own system, among other things, adjusting library search paths.
A user can generally tweak LD_LIBRARY_PATH
and /etc/ld.so.conf
, both of which are with lower precedence than DT_RPATH
, i.e. you can't override what is hardcoded in the binary, whereas if you use DT_RUNPATH
instead, a user can override it with LD_LIBRARY_PATH
.
(FWIW, I think ld.so.conf
should also take precedence over DT_RUNPATH
, but, anyway, at least we've got LD_LIBRARY_PATH
).
Also, I strongly disagree with the suggestion above to use DT_RPATH
. IMO, its best to use neither DT_RPATH
nor DT_RUNPATH
in shipped binaries.
unless
you ship all your dependent libraries with your executables and wish to ensure that things JustWork(tm) after installation, in this case use DT_RPATH
.