[OE-core] non-standard library locations and rpath

[Jack Mitchell]

On 05/12/16 16:43, Khem Raj wrote:
> On Mon, Dec 5, 2016 at 2:54 AM, Jack Mitchell <ml at embed.me.uk> wrote:
>>
>>
>> On 05/12/16 10:44, Jack Mitchell wrote:
>>>
>>> On 02/12/16 07:08, Khem Raj wrote:
>>>>
>>>> On Thu, Dec 1, 2016 at 8:18 AM, Jack Mitchell <ml at embed.me.uk> wrote:
>>>>>
>>>>> I'm having some troubles with shared library, shared library
>>>>> dependencies
>>>>> and rpaths. I have libfoo, which depends on libbar when I try to link
>>>>> libfoo
>>>>> with my app, it requires libbar to be found. libbar is in a non-standard
>>>>> location, /usr/local/bar when I compiled libfoo, I used -Wl,rpath-link
>>>>> ${STAGING_SYSROOT}/usr/local/bar and -Wl,rpath /usr/local/bar. Now
>>>>> when I
>>>>> come to try link my app with libfoo, it fails to link as it can't find
>>>>> libbar, which I assume means the rpath in libfoo isn't being properly
>>>>> prepending with sysroot what is the proper way to support this in OE? My
>>>>> library has the following rpath information:
>>>>>
>>>>> 0x0000000f (RPATH) Library rpath: [$ORIGIN/../lib:/usr/local/bar]
>>>>>
>>>>> So why isn't the rpath being prepended with the sysroot when I
>>>>> compile my
>>>>> app and link libfoo? The apps build system is using cmake, but this
>>>>> should
>>>>> be a built in linker feature, correct?
>>>>
>>>>
>>>> Only first path ( before :) is relative to location of binary at runtime
>>>>
>>>
>>> Exactly, so how can you make an OE build use the rpaths of libs that
>>> point to the build sysroot. What I have at the moment is
>>>
>>> 0x0000000f (RPATH) Library rpath: [$ORIGIN/../lib:/usr/local/bar]
>>>
>>> Which would be correct if I was linking on the target. However when OE
>>> sees the rpath in it's cross compile environment it should prepend it
>>> with the build sysroot so you end up with something like
>>>
>>> 0x0000000f (RPATH) Library rpath:
>>> [$ORIGIN/../lib:/path/to/build/sysroot/usr/local/bar]
>>>
>>> And then the SDK should end up with something like
>>>
>>> 0x0000000f (RPATH) Library rpath:
>>> [$ORIGIN/../lib:/path/to/sdk/sysroot/usr/local/bar]
>>>
>>> Is this what is expected to happen, or am I stumbling into an
>>> unsupported scenario.
>>>
>>> Cheers,
>>
>>
>> I think basically what I'm saying is that does the linker prepend it's
>> --sysroot value to absolute rpaths, and if not, should it?
>
> having absolute build paths into rpaths is not a good thing. Linker
> will search the libs during link in sysroot its configured to do so.
>

Ok, that makes sense. So something like this would be more appropriate?

rel_path = relative_path(mylib, otherlib)

-Wl,-rpath $ORIGIN${relpath}