Re: Suspicious warning in W64 build

[Paul Eggert]

Eli Zaretskii wrote:
> > 18446744065119617024 is 1<<64.
> > The other number is (1<<64) - (1<<33) - (1<<2).
> Yes, I know.  I just don't understand why GCC things that
>
>     nglyphs * sizeof (WORD) * 2
>
> can have a value in this range.  The type of nglyphs is 'int', and
> sizeof(WORD) gives 2.  So the range should be between 0 (or 4) and 4
> times INT_MAX, which is nowhere near the values GCC displays.

If nglyphs is negative the first multiplication is done using unsigned 
arithmetic, which could result in huge results. Presumably GCC does not know 
that nglyphs must be nonnegative. Try putting an 'eassume (0 <= nglyphs);' 
before the line in question. That is, if you're sure that nglyphs is 
nonnegative: if you're not, GCC has found a real bug here.