Paul Herring wrote:
> On 8/31/07, Thomas Hruska <[EMAIL PROTECTED]> wrote:
>
>> error C2511: 'MyBase2 *MyDerived::Copy(void)' : overloaded member
>> function not found in 'MyDerived'
>
> It appears to have something to do with the const qualifiers -
> removing the three from your example allows the code to compile. Why
> this is so, and whether it helps you I'm not too sure...
Oooookay...that's even weirder. It definitely helps (i.e. it works for
now). But that seems oddly like a bug. Why would dropping 'const'
cause it to compile? I wasn't doing anything non-const in the example
that I'm aware of. And the problem only appeared when two base class
_paths_ (for lack of a better word) had a Copy() - using const was fine
when there was only one base class path.
I just ran the original code through the Comeau C++ online compiler with
their latest alpha/beta version (4.3.9) and it compiled fine under
strict mode.
ANSI Standard Draft (I'm still too cheap :P) references:
--------------
In this International Standard, the notation cv (or cv1, cv2, etc.),
used in the description of types, represents an arbitrary set of
cv-qualifiers, i.e., one of {const }, {volatile }, {const, volatile}, or
the empty set. Cv-qualifiers applied to an array type attach to the
underlying element type, so the notation cv T, where T is an array type,
refers to an array whose elements are so-qualified. Such array types can
be said to be more (or less) cv-qualified than other types based on the
cv-qualification of the underlying element types.
Table 7: relations on const and volatile
no cv-qualifier < const
no cv-qualifier < volatile
no cv-qualifier < const volatile
const < const volatile
volatile < const volatile
--------------
--------------
The return type of an overriding function shall be either identical to
the return type of the overridden function or covariant with the classes
of the functions. If a function D::f overrides a function B::f, the
return types of the functions are covariant if they satisfy the
following criteria:
- both are pointers to classes or references to classes(104)
- the class in the return type of B::f is the same class as the class
in the return type of D::f, or is an unambiguous and accessible direct
or indirect base class of the class in the return type of D::f
- both pointers or references have the same cv-qualification and the
class type in the return type of D::f has the same cv-qualification as
or less cv-qualification than the class type in the return type of B::f.
(104) Multi-level pointers to classes or references to multi-level
pointers to classes are not allowed.
--------------
As far as I can tell, the original code should work based on what I'm
reading above. Everything had the same cv-qualifier and I wasn't doing
anything non-const'ish. Additionally, given that the "most
Standards-compliant compiler" (Comeau C++) compiles my code, I say this
is a compiler bug.
I just asked around. Apparently the original code works fine in VS.NET
2005. I'm still going to wait for "Orcas" before upgrading.
--
Thomas Hruska
CubicleSoft President
Ph: 517-803-4197
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