Embed RPATH instead of RUNPATH in when building shared-objects on Ubuntu 18.04

Question

I have a Linux shared-object, which links dynamically with some shared-objects, and some of them in turn link dynamically further with additional shared-objects, requiring indirect dynamic linking. To find those SOs I embed an RPATH header into my top-level SO by passing linker flags to G++ as in:

 -Xlinker -rpath -Xlinker $ORIGIN/../my/libs

This works on both Ubuntu 16.04 and CentOS 7.x (with G++ 7.3 from DevToolset 7). However, when performing this build on Ubuntu 18.04, it embeds a RUNPATH header instead. Unlike RPATH, RUNPATH is only considered for finding SOs required by my top-level SO, but not for indirect dynamic linking of subsequent SOs that they require.

I've confirmed that the change from RPATH to RUNPATH causes the issue. When I use an SO built on Ubuntu 16.04, that has an RPATH header, indirect linking works properly. When I change the RPATH header to a RUNPATH header using chrpath -c, indirect linking breaks, on both Ubuntu 18.04 and Ubuntu 16.04.

How can I get the linker to use RPATH on Ubuntu 18.04? Alternatively, how can I accomplish the inverse of chrpath -c - change a RUNPATH header into an RPATH?

Possible duplicate of Dynamic linking with rpath not working under Ubuntu 17.10 — Employed Russian
– Employed Russian, Commented Aug 22, 2018 at 1:53
@EmployedRussian - I've narrowed the scope of the question to only deal with creating an RPATH header. — Isac Casapu
– Isac Casapu, Commented Aug 23, 2018 at 12:05
Wow, this question answers the problem I have (I was wondering about the difference of the indirect links based on the expirience, but was not able to find any info on it). — xvorsx
– xvorsx, Commented Jan 15, 2023 at 17:33

Employed Russian · Accepted Answer · 2018-08-23 14:34:27Z

6

How can I get RUNPATH to be passed down to subsequent SOs during indirect linking?

As explained in this answer, you can't.

The best approach is to fix all libraries to be self-sufficient (have their own correct RUNPATH).

If you can't do that, use RPATH instead of RUNPATH, by adding -Wl,--disable-new-dtags to the link line.

edited Aug 23, 2018 at 14:34

answered Aug 22, 2018 at 1:58

Employed Russian

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becker33 · Accepted Answer · 2024-07-18 22:43:43Z

0

There is no good tool to do this, but you can manually edit the DT_RUNPATH byte of the dynamic section of the elf binary to 0, which will reverse the change of behavior.

answered Jul 18, 2024 at 22:43

becker33

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