Re: Multi-arch

["Dr. Adrian Wrigley" <amtw@linuxchip.demon.co.uk.uk.uk>]

On Thu, 18 May 2006 21:24:44 +0000, Bj�rn Persson wrote:

> I understand how multi-arch is useful if you want to use proprietary 
> binaries that are available only for certain architectures. Otherwise I 
> don't see a reason to do it. I'd think free code would just be compiled 
> for the "native" architecture. Is multi-arch useful in an altogether 
> free system in some way that eludes me?

Several reasons.

I suggest that people who run a mixture of machines may want
to share binaries across the network, but build them on their
newest machines.

People also want to avoid recompiling working code with another
architecture, even if they have source code.  You can't be sure
it'll work exactly right without testing, which may be expensive.
I found a couple of latent errors when builing for 64-bit.
One was calling a C varargs function incorrectly from Ada.
Another was caused by undocumented members of a C struct
overwriting the Ada stack.  Changing architectures is a risk.

If you have written some code in assembly language, this will
constrain the architecture until alternative code is available.

Finally, some people store records directly in data files
for various reasons.  Changing architecture would need
recreatoin of those files.

It only takes one old architecture library to be a show-stopper,
whether that is a third-party or handwritten codec, a buggy
library or whatever. 

multi-arch eases the transition to a new architecture.
--
Adrian