About this code / suggested patch :
>> We don't need to modify the mainline Emacs code in order toAs Fabrice explained, the warning is about code that is never executed
>> pacify third-party compilers that issue incorrect warnings.
>
> What is incorrect about that warning?
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.