Prepend to RPATH

Question

After building with CMake on Linux (but before installing), all the linked libraries are added to the final executable's RPATH.

However, I would like to prepend $ORIGIN/../lib: to this RPATH.

So far, I've only been able to replace the RPATH, and that's not what I want: I want ld.so to first look in ../lib. This is what I currently do:

set_target_properties(foo PROPERTIES
  BUILD_WITH_INSTALL_RPATH TRUE
  INSTALL_RPATH "\$ORIGIN/../lib:...")

While this works, it's missing some additional third-party libraries that are not part of my build tree, and who are not located in system directories.

Doing chrpath -l foo gives me the exact same INSTALL_RPATH above. If I don't set those properties, I get the long list of DSO locations, e.g. RPATH=/bar/baz/:/quux/ etc. (the one I'd like to prepend to).

I've tried using get_property(_existing_rpath foo INSTALL_RPATH), but that gives me an empty string

I've read the hints at https://cmake.org/Wiki/CMake_RPATH_handling and noticed under "CMake Bugs" that

At least on CMake 2.6.4 RHEL5, man cmakecommands for INSTALL_RPATH_USE_LINK_PATH pretends that this setting will append the link path to any CMAKE_INSTALL_RPATH content one specified. However, on this version, enabling INSTALL_RPATH_USE_LINK_PATH will replace it.

Well, not so sure about this any more: just verified this on CMake 2.8.0, and now on both versions it does list correct changes in cmake_install.cmake. This bug may have occurred due to previously not doing per-target install(), or perhaps due to some other changes in CMake RPATH-related variables.

By the way, I'm only interested in getting a working RPATH for the built files, as in before having run install. I haven't configured the installation properly (added install targets and so on). Do I need to look into that part for this to work?

Answer 1

If you can't find answers on Google, it's often the case that the answer is obvious. This seems to work just fine:

set_target_properties(foo PROPERTIES
  BUILD_WITH_INSTALL_RPATH TRUE
  INSTALL_RPATH_USE_LINK_PATH TRUE
  INSTALL_RPATH "\$ORIGIN/../lib:${INSTALL_RPATH}")

On my system (and CMake 3.6.1), it seems INSTALL_RPATH begins with a colon, but I wouldn't count on it. Also, since I'm obviously setting the global INSTALL_RPATH here, it may be overspecified (I haven't checked).