Distributions still suffering from s390 ABI change problems.

[Rich Felker]

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