Re: [boost] Re: is_convertible corner case

From: Howard Hinnant (hinnant_at_[hidden])
Date: 2003-01-25 10:47:53

On Saturday, January 25, 2003, at 08:39  AM, Peter Dimov wrote:

>> Furthermore, it is undefined to pass a non-pod to an ellipse 
>> (5.2.2/7):
>>
>> int  foo(...);
>>
>> class B
>> {
>> public:
>> B();
>> private:
>> B(const B&);
>> };
>>
>> int main()
>> {
>> foo(B());  // undefined behavior
>> }
>>
>> If you stick that in a sizeof, it is still undefined:
>>
>> sizeof(foo(B()));
>
> Is it?
>
> if(false) foo(B());
>
> Is this undefined too?

<shrug> That's the way I read 5.2.2/7.  I see little difference between 
that example and:

class B
{
        int foo();
};

int main()
{
        B b;
        if (false)
                b.foo();
}

Except in the latter a diagnostic is required, whereas a diagnostic is 
not required, only permitted in the former.

I'm open to other interpretations.  Note that 1.3.12 defines undefined 
behavior, and specifically includes a compile time diagnostic and 
termination of compilation as possible consequences of undefined 
behavior (i.e. undefined behavior includes compile time behavior, not 
just run time behavior).

-Howard