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From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
Message-Id: <200203022210.XAA05451@father.ludd.luth.se>
Subject: Re: libm signed/unsigned warnings
In-Reply-To: <8011-Sat02Mar2002205420+0200-eliz@is.elta.co.il> from Eli Zaretskii at "Mar 2, 2002 08:54:20 pm"
To: djgpp-workers AT delorie DOT com
Date: Sat, 2 Mar 2002 23:10:35 +0100 (MET)
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According to Eli Zaretskii:
> > From: Martin Str|mberg <ams AT ludd DOT luth DOT se>
> > -                   if((j<<(52-k))==ly) yisint = 2-(j&1);
> > +                   if((((__uint32_t)(j))<<(52-k))==ly) yisint = 2-(j&1);
> 
> This seems okay, but is mighty ugly.  Can you find a better way of
> shutting up GCC in this case?

Perhaps. But I'd really like somebody who understands the code to make
more extensive changes.

> > -               if(((t1&sign)==sign)&&(s1&sign)==0) s0 += 1;
> > +               if((t1&sign)&&(s1&sign)==0) s0 += 1;
> >                 ix0 -= t;
> >                 if (ix1 < t1) ix0 -= 1;
> >                 ix1 -= t1;
> > 
> > __int32_t sign = (int)0x80000000U;
> > __uint32_t t1,s1;
> > 
> > (t1&sign)==sign checks if the sign bit is set or not. The comparision
> > with sign should be uneccessary.
> 
> I don't understand the original problem here: both t1 and sign are
> int's, so why does GCC complain?  What is the exact language of the
> warning?

No. t1 is unsigned.

> > -               if(ix>0x80000000U) z = (invsqrtpi*cc)/__ieee754_sqrtf(x);
> > +               if((__uint32_t)ix>0x80000000U) z = (invsqrtpi*cc)/__ieee754_sqrtf(x);
> 
> I tend to think that this is a bug in the original code, since ix is
> computed a few lines above this like so:
> 
> 	ix = hx&0x7fffffff;
> 
> So its high bit can never be set, and the comparison should always
> fail.  Am I missing something?

I'm missing which file we're talking about...

> Perhaps you could add a call to abort() into that if clause, and see
> if it ever gets called when you run the cygnus test suite from djtst.

Anyway the abort() is a good idea.


Right,

						MartinS