Date: Mon, 28 Jan 2019 10:29:12 -0500 From: Rich Felker <dalias@...c.org> To: musl@...ts.openwall.com Subject: Re: (OT?) Re: Symbol versioning approximation trips on compat symbols On Mon, Jan 28, 2019 at 02:08:13PM +0100, u-uy74@...ey.se wrote: > On Mon, Jan 28, 2019 at 07:34:25AM +0100, Florian Weimer wrote: > > * u-uy: > > > > > On Sat, Jan 26, 2019 at 11:04:24PM -0500, Rich Felker wrote: > > >> For what it's worth, compat symbols would have let us remove symbols > > >> that shouldn't have been put in musl, such as lchmod (which confuses > > >> broken apps which wrongly expect that, if it exists, it should work) > > > > > > For what my integrator perspective is worth, exposing brokenness instead > > > of catering for it is a Good Thing. > > > So far, no one has presented a compelling way how to test for symbol > > versioning support. > > My comment apparently fell out of context. Sorry for that. > > It was about applications who make undue assumptions (and as a consequence > use misdirected tests). Exposing the failures of those assumptions is > vital to be able to make it better. > > If there is a feature which is hard or impossible to test for, like > symbol versioning, it means that the applications may _have_ to rely on > an explicit build flag telling whether to use it. > > IOW it is for the most part not a technical problem but rather a problem > of awareness among application developers. It wouldn't be hard to test for if toolchains had been consistent with musl capabilities all along. They have not been. So we have a situation where the valid build-time tests indicate support, but runtime silently lacks it. I don't think this is a good situation to have created, and it's not fixable by telling the toolchains "no, we don't actually have that" because there are and will be deployed toolchains that don't know/honor that for a long time. Fortunately, it mostly doesn't matter since the main intended usage for versioning is to link to the current/default version symbols, assuming your apps are all up-to-date with respect to your libs (and libs wrt each other). But I still think honoring version bindings in ldso is the right course of action. Rich
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