Missing asm constraint exposing compiler version differences

[Andrew Haley]

On 08/28/2010 08:41 PM, Philip Prindeville wrote:
>  Hi.
>
> I work a bit with Asterisk, the IP-PBX open software.  There's a GSM
> library that's included in the source tree.
>
> The problem we're encountering is that when compiled with gcc 4.1.x and
> 4.3 or later, it works fine.
>
> But some of our target platforms only support gcc 4.2, and when we
> compile against this, the optimizer in GCC exposes the fact that someone
> writing some ASM stubs forgot to correctly annotate a constraint, and
> that lack of a constraint is causing the optimizer to change the
> generated object more than it should.
>
> There are a lot of lines of source code, and most of my experience with
> asm() stubs has been rudimentary, so I'm asking for an outside pair of
> eyeballs that might be better skilled at identifying how the asm should
> be annotated than me.

How do you know that the asm is the problem?

Andrew.