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Re: Distributions still suffering from s390 ABI change problems.
- From: Rich Felker <dalias at libc dot org>
- To: Carlos O'Donell <carlos at redhat dot com>
- Cc: David Miller <davem at davemloft dot net>, aurelien at aurel32 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 01:00:09 -0400
- 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>
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 design is fully immune to any need for ABI change when expanding
the size of the state setjmp has to preserve.
Rich