Private/protected inheritance problem

From: Mark A. Gibbs (x_gibbsmark_at_rogers.com_x)
Date: 03/12/05 

Date: Fri, 11 Mar 2005 22:26:13 -0500

Good day,

i'm having a bit of trouble with a base class i'm working on. this is
what it boils down to:

template <typename T>
class foo
{
protected:
    foo() { T* p = static_cast<T*>(this); }
};

class bar : foo<bar>
{
public:
    bar() {}
};

as is bar inherits privately from foo, and i get a compile error on the
assignment saying "Illegal access from bar to private/protected member
foo::" (that's exactly what it says, just "foo::").

when i use public inheritance, there's no problem. however, i get the
same problem for protected inheritance, or when i make foo::foo() a
public constructor.

is there a reason for this? i mean, when foo::foo() is instantiated, the
relationship between foo and T is known and clear. i don't see what
private member of foo bar is trying to access. i tried making a
workaround by doing this:

int distance = static_cast<foo<T>*>((T*)0);
T* p = reinterpret_cast<T*>(this - distance);

but it still failed on the first line.

i'm using codewarrior 8. what i want to do is get a pointer to the
derived class from the base class. 

-- 
Mark A. Gibbs (aka. Indi)
Administrator
#c++ on irc.Rizon.net
http://ca.geocities.com/indij@rogers.com/
(temporary website)

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