Re: [gentoo-user] [OT] How to add library to dynamically linked executable?

[Bryan Gardiner <bog@khumba.net>]

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On Mon, 22 Jun 2015 16:13:57 +0000 (UTC)
Grant Edwards <grant.b.edwards@gmail.com> wrote:

> Is there any way to add a library to the list of libraries required by
> an ELF dynamically linked executable?
> 
> I have an executable (let's call it "foo") which was written and built
> by somebody else [I don't have sources].  It requires the librt to run
> on one particular platform, but librt isn't in the exeuctable's list
> of libraries.  [I'll skip the story of how it ended up this way. It
> will be fixed with the next version of that application.]
> 
>   # foo
>   foo: can't resolve symbol 'shm_open'
>   
> If I run it like this, it's fine:
> 
>   # LD_PRELOAD=/lib/librt.so.0 foo
> 
> Is there any way to fix the ELF executable file to add librt.so.0 to
> its list of libraries?
> 
> I'm aware I can create a shell script that does this:
> 
> #!/bin/sh
> export LD_PRELOAD=/lib/librt.so.0
> exec foo
> 
> What I'm wondering about is whether there is a way to fix the ELF
> executable file itself so as to add librt.so.0 to its list of shared
> libraries.  I've found chrpath(1), but it only changes the search path
> used to look for libraires, not the list of libraries themselves.
> 

Perhaps elfsh[1] would do the trick.  There's an example[2] that
demonstrates editing the dynamic section, so you might be able to add
an entry that way, though it's not as simple as an "addneeded"
command.  Although it sounds[3] like elfsh might not be very stable.

Actually, scratch all that, NixOS's patchelf command[4] supports
editing NEEDED entries now, that'll be the easiest way.

Cheers,
Bryan

[1] http://www.eresi-project.org/wiki/TheELFsh
[2] http://www.eresi-project.org/browser/trunk/testsuite/elf/elf-tests.esh
[3] https://stackoverflow.com/a/2287737
[4] https://github.com/NixOS/patchelf

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