Re: [boost] Portable signbit macro/function?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2006-08-04 07:12:44

Martin Bonner wrote:
>> Johan Råde wrote:
>>
>>> I still find it hard to believe that the volatile are needed ;-)
>>
>> It is not.
>
> If volatile is not present, then you can't instantiate the template
> with T="volatile float" for example. (Similarly you need the "const"
> so that you can invoke with T="const float".)

template<class T, class S> T binary_cast( S const & s )
{
    T t;
    memcpy( &t, &s, sizeof(T) );
    return t;
}

You need the const on s to be able to pass rvalues such as 1.0, not for 
const lvalues. It is true that binary_cast will fail to compile if you pass 
a volatile object as source, this is intentional; accessing a volatile 
object as a sequence of bytes can be dangerous if that volatile object is an 
I/O port.

You definitely don't need a volatile on t, it only inhibits useful 
optimizations.