[CMake] cmake end user vs. developer rpath handling

[Eric Noulard]

Le jeu. 10 oct. 2019 à 14:30, Eric Noulard <eric.noulard at gmail.com> a
écrit :

>
>
> Le jeu. 10 oct. 2019 à 14:02, Zakrzewski, Jakub <
> Jakub.Zakrzewski at scheer-group.com> a écrit :
>
>> ------------------------------
>> *From:* CMake <cmake-bounces at cmake.org> on behalf of Eric Noulard <
>> eric.noulard at gmail.com>
>> *Sent:* 10 October 2019 12:05
>> *To:* DIXON, MARK C.
>> *Cc:* cmake at cmake.org
>> *Subject:* [DKIM] Re: [CMake] cmake end user vs. developer rpath handling
>>
>>
>> > No they can't because the maximum size is burried into the binary ELF
>> file,
>> > that why CMake "reserve" some space with many ";;;" in order to replace
>> BUILD_RPATH with INSTALL_RPATH when doing
>> > 'install'.
>>
>> Interesting.
>> So you're saying that this:
>> https://github.com/NixOS/patchelf/blob/8cc2d64444b0946abb0009058865cd46165b69c4/src/patchelf.cc#L1288-L1319
>> does not really work? (An honest question)
>>
>
> Nope I meant that my manual page forr chrpath says:
>        -r <path> | --replace <path>
>               Replace current rpath or runpath setting with the path
> given.  The new path must be shorter or the same length as the current path.
>
> patchelf does not seem to have this limitation.
> I remember trying and being hit by that issue, but I did not tried it
> recently.
> I'll try again and come back to you.
>

with chrpath try to replace an rpath with a longer one I get:
new rpath '/../lib:/purposely/too/long/rpath/hdsjds/dshkjhdsk/dsgdjsj' too
large; maximum length 104

with patchelf is works with an intriguing warning:
warning: working around a Linux kernel bug by creating a hole of 2093056
bytes in ‘/path/to/executable’

which seems to be a resolved issue:
https://github.com/NixOS/patchelf/issues/92

after that on the modified executable,
chrpath is printing weird output when asking to read rpath.
patchelf does properly print modified rpath.

I think the SO article gives enough reference for this:
https://stackoverflow.com/questions/13769141/can-i-change-rpath-in-an-already-compiled-binary

So I was wrong, thank you for your honest question Jakub.
I learned something usefull thanks to you.


-- 
Eric
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