On Tue, 2021-06-01 at 07:58 -0700, Khem Raj wrote: > > On 5/31/21 3:40 PM, Paul Eggleton wrote: > > Hi folks > > > > Upstream in the systemd project, a proposal has been made to add a special > > section to output ELF binaries to record soft runtime dependencies, so that > > they could be read and utilised by distribution build systems such as ours > > (they would be translated into RRECOMMENDS in our case). At the moment that > > doesn't seem to have generated a huge amount of interest in the traditional > > distro space, but would it be interesting for us? > > > > https://github.com/systemd/systemd/pull/17416 > > > > For clarity, we (Microsoft) will volunteer to do the integration assuming > > the > > above pull request gets reopened and merged, which is more likely if we > > express our interest. > > Finding dlopen dependencies is a neat idea, but it has to be accepted > cross distro, and also applications have to manually declare it in code > if I understand systemd's patch correctly. This will be hard to > accomplish as you can see changes are spread across apps from distro > point of view. Perhaps there is a smarter way of detecting adding them > in ELF spec itself and then have tools like linker help implement this > and also possibly collect the information or guide the users to achieve > this would be helpful.
Yes ideally ELF shared objects/the linker/the loader would support weak symbols (like dylib on OSX). Unfortunately they do not, and it seems there's no interest to add it becasue there's no concrete use case that shows it's useful. But that cannot happen until there's some support for it. Chicken and egg... There have been lots of theoretical discussions about pros and cons, and my hope was that if at least one distro could find it useful, and could show that it is in practice useful and the theoretical issues are not that problematic and could be solved, others would follow suit. So leaving aside other distros, is this something that would concretely benefit the Yocto project for handling the systemd recipe? There are currently 12 dlopen()-based optional dependencies in systemd, and the number grows with each release. -- Kind regards, Luca Boccassi
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