Re: warnings compiling Emacs 22 on amd64

[Eli Zaretskii]

> Cc: Francesco Potorti` <address@hidden>,  address@hidden
> From: Stefan Monnier <address@hidden>
> Date: Mon, 11 Dec 2006 17:52:44 -0500
> 
> If the argument i is of type int (32bit), then the compiler is sufficiently
> clever to infer that the comparisons will always return the same value
> (even though we cast that value to EMACS_INT (64bit) in between).

Is it really that smart?  Will it also be that smart if we do some
arithmetics, like `(EMACS_INT)i + 0L' or `(EMACS_INT)i*1L'?

> > If FIXNUM_OVERFLOW_P should always return zero on 64-bit machines,
> 
> It shouldn't.  There are a few sites where it does, tho.

Are these few cases those for which the argument of FIXNUM_OVERFLOW_P
is an int (rather than a long)?

> > Does this fix the problem?
> 
> What problem?

The warning messages.

> There is no problem other than unhelpful warnings.
> The warnings basically say "hey guys, I found an optimization opportunity"
> and we're very happy that gcc does the optimization: it saves us from trying
> to write ugly and brittle code such as the one above.  Too bad gcc is a bit
> noisy in this case.  We can probably remove those warnings with the
> right -Wno-foo invocation.

I don't think we want to remove this warning in general with -W-no-*
because it could point out bugs, and I don't think we like to see
warnings where the code is correct.  You are free to think otherwise,
of course, but please let us try to resolve that anyway.