Re: code question

[JD <jd1008 at gmail dot com>]

On 09/26/2012 11:17 PM, Ian Lance Taylor wrote:
> On Wed, Sep 26, 2012 at 10:07 PM, JD <jd1008@gmail.com> wrote:
> > On 09/26/2012 10:46 PM, Ian Lance Taylor wrote:
> > > On Wed, Sep 26, 2012 at 6:18 PM, JD <jd1008@gmail.com> wrote:
> > > > I came across this patch which could be cause of a bug.
> > > >
> > > > What are possible side effects of this
> > > > code segment if compiled under various
> > > > non-gnu C compilers, and GCC compilers?
> > > >
> > > > > +inline uint32_t NS_MIN(uint32_t a, uint64_t b)
> > > > > +{
> > > > > +  return b < a ? b : a;
> > > > > +}
> > > > Nit: Please cast the 64-bit variable to 32-bit in case compilers start
> > > > warning about it.
> > > >
> > > > > +      *pProgress = NS_MIN<PRUint64>(totalBytes - bytesLeft,
> > > > > PR_UINT32_MAX);
> > > It's very hard to determine the behaviour of an incomplete program.
> > > It's even harder when you show us two incompatible code fragments.
> > > You are defining a non-template function NS_MIN and calling a template
> > > function NS_MIN.  I would expect a compiler error.  I don't know what
> > > you are seeing.
> > >
> > > The basic groundrules for this kind of question are: tell us precisely
> > > what you did, tell us precisely what happened, and tell us what you
> > > expected to happen instead.
> > >
> > > Ian
> > I was hoping to see what programmers would have to
> > say about comparing unsigned 32 bit with unsigned 64 bit
> > in the line
> >
> >
> > return b < a ? b : a;
> >
> > does the C compiler first promote the 32  bit  to 64 bit before the
> > comparison
> > or vice versa - the 64 bit demoted to 32 bit before comparison.
>
> Please reply to the mailing list, not just to me.  Thanks.
>
>
> if you compare an unsigned 32-bit value to an unsigned 64-bit value,
> the unsigned 32-bit value will be zero-extended to 64-bits, and the
> values will be compared as unsigned 64-bit values.
>
> Ian
Thanx - but,re responding - Thunderbird did that when I clicked on Reply.
It replied to you instead of mailing list. Sorry about that. Will watch 
for it
next time.
Re: zero extending the 32 bit value by the compiler before comparison.
Is it zero extended on left or on right?

Thanx,

JD