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Re: Windows 64 port

From: Paul Eggert
Subject: Re: Windows 64 port
Date: Wed, 29 Feb 2012 11:43:28 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1

>> We don't need to modify the mainline Emacs code in order to
>> pacify third-party compilers that issue incorrect warnings.
> What is incorrect about that warning?

As Fabrice explained, the warning is about code that is never executed
on his platform, because it's inside a conditional that is always
false, and so the bug cannot possibly occur.

The conditional itself is a constant, and decent compiler
will optimize away the code in question.  The conditional is present
precisely to avoid the overflow that the compiler is mistakenly warning
about.  There is no easy way to rewrite the code that will both
pacify the broken compiler and keep the code modular and portable.

Cases like these are an an easy call: leave the code alone and
ignore the bogus warning.  If possible, pass a flag to the compiler
telling it not to issue bogus warnings like that.  Or get the
compiler bug fixed.  Whatever.

> If some compiler tells us something valuable about the code, we
> need not ignore it just because it's "third-party".

True, but it appears that many of the fixes in his patch are to
pacify warnings like the above.  That is, it appears that a class
of warnings are often bogus and do not correspond to real bugs.
This is an easy call: leave the code alone.

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