Re: [boost] Re: compressed_pair requirements?

From: John Maddock (john_at_[hidden])
Date: 2005-05-28 11:28:24

> Umm... yeah!  And what was the error on Intel with the const empty type? 
> ;-)

It was something useful like "Illegal base class".

> This is a pretty interesting point.  I whipped this test up to explore:
>
> struct Base {};
>
> typedef const Base ConstBase;
>
> struct A
>     : ConstBase
> {
>     A() {}
> };
>
> It compiles on CW.  But it doesn't on Comeau C++ Online (thanks Greg). 
> Normally when CW and EDG disagree, the decision usually goes to EDG.  So I 
> started searching the standard for where it says that cv-qualified classes 
> can't be used as base specifiers so that I could send our compiler team 
> the bug report.
>
> Couldn't find it.  So I started digging into the core issues list and 
> found:
>
> http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_closed.html#484
>
> Subject:  Can a base-specifier name a cv-qualified class type?
>
> Ah, perfect.
>
>> The resolution of issue 298 added new text to 9.1   class.name paragraph 
>> 5 making it clear that a typedef that names a cv-qualified class type is 
>> a class-name. Because the definition of base-specifier simply refers to 
>> class-name, it is already the case that cv-qualified class types are 
>> permitted as base-specifiers.
>
> No kidding.  And check out the date on that:
>
>> Rationale (April, 2005):
>
> Fresh from the Lillehammer presses! :-)

Right, but it's been declared a duplicate of issue 298, which was resolved 
in April 2003, so it's that remarkable thing, an EDG deviation from the 
standard.

Well researched!

John.