Re: LINKER_USE_RPATH ignored on darwin systems

[Michael Davidsaver via Core-talk <core-talk at aps.anl.gov>]

On 11/21/24 16:22, Colby Sparks via Core-talk wrote:
> I am building a motor driver which makes use of a 3rd party library
> that requires its runtime load path be specified during linking.
>
> For linux builds this works fine. If LINKER_USE_PATH=YES, then the
> build system will add rpath arguments for all of the libs in
> PROD_DEPLIB_DIRS
> (https://urldefense.us/v3/__https://github.com/epics-base/epics-base/blob/b7cc33c3c9c1a6cc14290b9a558e97bd89171e80/configure/os/CONFIG.Common.linuxCommon*L26-L27__;Iw!!G_uCfscf7eWS!aQd1UvUH3P8dEftuqQH-HKm-bSaFaUum_-Rbr4CXcTjCNXcCMGwnJd665ADvo-z9AGElFxGyMqYTQFWiMSzxAGm2xBE$ ).
> For darwin builds, however, it seems that the default build
> configuration ignores LINKER_USE_RPATH and will never add rpaths. This
> means an IOC which uses my driver will fail to load its shared libs at
> runtime.
>
> I could add the following to my example IOC's CONFIG_SITE file and
> make a note that users do the same:
>
> ifneq ($(filter darwin-%, $(T_A)),)
> PRODDIR_RPATH_LDFLAGS_YES += $(PROD_DEPLIB_DIRS:%=-Wl,-rpath,%)
> PRODDIR_LDFLAGS += $(PRODDIR_RPATH_LDFLAGS_$(LINKER_USE_RPATH))
> endif
>
> But I am wondering if this is ill-advised. I am not very familiar with
> the EPICS build system, so I imagine that there is a better way to
> make this work.
If the executable links and runs, that seems promising :)

When dealing with a, presumably closed source, 3rd party library
it isn't surprising to need to jump through some additional hoops.


> I am also curious why LINKER_USE_RPATH is ignored by
> default when building for macOS.
So far no one has been motivated enough to make it work.
aka. PRs welcomed.

As a note on some ELF vs. Mach-o differences, I have found that
understand '-rpath' with Mach-o also required understanding the
differences between '-soname' vs. '-install_name'.