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Re: Distributions still suffering from s390 ABI change problems.
- From: Aurelien Jarno <aurelien at aurel32 dot net>
- To: Rich Felker <dalias at libc dot org>
- Cc: Carlos O'Donell <carlos at redhat dot com>, David Miller <davem at davemloft dot net>, Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>, siddhesh at redhat dot com, allan at archlinux dot org, libc-alpha at sourceware dot org
- Date: Tue, 15 Jul 2014 12:35:32 +0200
- Subject: Re: Distributions still suffering from s390 ABI change problems.
- Authentication-results: sourceware.org; auth=none
- References: <20140713182420 dot GA14513 at hall dot aurel32 dot net> <20140714052022 dot GR609 at spoyarek dot pnq dot redhat dot com> <20140714072228 dot GF1239 at hall dot aurel32 dot net> <20140714 dot 002520 dot 985400136122770421 dot davem at davemloft dot net> <53C40A5A dot 5050202 at redhat dot com> <20140715050009 dot GU179 at brightrain dot aerifal dot cx>
On Tue, Jul 15, 2014 at 01:00:09AM -0400, Rich Felker wrote:
> On Mon, Jul 14, 2014 at 12:50:34PM -0400, Carlos O'Donell wrote:
> > On 07/14/2014 03:25 AM, David Miller wrote:
> > > From: Aurelien Jarno <aurelien@aurel32.net>
> > > Date: Mon, 14 Jul 2014 09:22:28 +0200
> > >
> > >> We can continue handling this ABI change by rebuilding all packages
> > >> dependind on libpng, but I am afraid that embedding a jmp_buf in a
> > >> structure is not that uncommon and that we are going to discover
> > >> more affected packages.
> > >
> > > This is a really serious mess.
> >
> > There was no other way around this, and our tooling sucks for detecting
> > mixed ABI usage and telling users how to fix it.
>
> Yes there was. No matter how much state setjmp needs to store, there
> is always a way to avoid ABI breakage as long as jmp_buf is at least
> the size of a pointer:
>
> #define setjmp(jb) __new_setjmp(jb, alloca(__get_real_jb_size()))
>
> Then the jmp_buf need only store a pointer to the caller-provided
> register-storage space.
This would work if jmp_buf was an opaque structure. It is not the case
and we can imagine code accessing its content. In that case it will
still break.
--
Aurelien Jarno GPG: 4096R/1DDD8C9B
aurelien@aurel32.net http://www.aurel32.net