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Date: Mon, 27 Jul 2020 14:57:10 -0600
From: Ariadne Conill <ariadne@...eferenced.org>
To: musl@...ts.openwall.com
Subject: Re: friendly errors for ABI mismatch
Hello,
On Monday, July 27, 2020 10:03:30 AM MDT Rich Felker wrote:
> On Mon, Jul 27, 2020 at 09:27:28AM -0600, Ariadne Conill wrote:
> > Hello,
> >
> > On 32-bit systems, musl 1.2 has a new ABI (due to time64). This results
> > in
> > programs built against musl 1.2 failing to run against musl 1.1. That
> > part is fine, but you get an error message about being unable to relocate
> > symbols, which is not really insightful if you don't know about the ABI
> > break.
> >
> > glibc, on the other hand, has a minimum version specified in every binary,
> > and prints an error message saying the glibc is too old if this situation
> > is encountered.
> >
> > I think we should add this feature to musl, so that in the future if we
> > have another ABI break, users will be given useful advice about how to
> > fix it. Due to the relocation error message, a few Alpine contributors
> > have been tripped up while trying to debug their work...
>
> What you're seeing here is just a special case of the general property
> that, if you've linked to a version of libc (or any library) that has
> a new symbol and attempt to run with an older version, you'll get a
> missing symbol error. It's very intentional (see libc comparison and
> "forward compatibility") that we don't encode "minimum version number"
> required anywhere. If you attempt to run with a library that has all
> the symbols, it will run, subject to any bugs in the library version
> you have and any functionality that returns with failure because it's
> not supported in the version you have, etc.
>
> There is no way to give a more high-level reason for the runtime link
> failure like "your program needs time64 and you're running with an old
> musl" because the code reporting the error *is the old musl* that's
> not aware of whatever it is that the new binary is missing. Maybe you
> have something else in mind that I don't fully understand, but
> whatever it is it would only address future missing symbol errors, not
> the ones you're seeing right now.
Simply what I have in mind is having friendly errors in the future, obviously
we cannot do it with time64.
Ariadne
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