Re: [gnugo-devel] sign bit bit shift issue

[dave . denholm]

Arend Bayer <address@hidden> writes:

> Hellwig wrote:
> 
> > On 08-Feb-03 Arend Bayer wrote:
> > >
> > > According to the C standard, the patch below fixes a bug. Rotating into
> > > the sign bit of a signed integer is undefined.
> > >
> > > Does anyone happen to know whether this is a problem in real world?
> > > (I.e. do there exist platforms where (1 << 31 == 0x8000000) does not
> > > hold true?)
> >


> This seems to say clearly that 1 << 31 is undefined for 32bit ints.
> 


Probably no less defined than

 (signed int)(1U << 31)


ie setting bit 31 in an unsigned int, then casting to signed


[
 Are the quantities concerned naturally signed ?  If bit shifting is
 going on, perhaps everything should be unsigned anyway ?
]


dd
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