Error about inaccessable class

In the code below gcc says

test.cpp: In constructor `SingleInfoDialog::SingleInfoDialog(const
PlayableSetBase&)':
test.cpp:2: error: `class PlayableSetBase' is inaccessible
test.cpp:24: error: within this context

Obviosly gcc does not manage to pass the parameter of type const
PlayableSetBase& to the constructor of InfoDialog because there is a
private base class with the same name. Is this really not allowed?


Marcel


-----
class PlayableSetBase
{
};

class OwnedPlayableSet
: public PlayableSetBase
{public:
OwnedPlayableSet(const PlayableSetBase& r);
};


class InfoDialog
// a member is not sufficient because of the destruction sequence
: private OwnedPlayableSet
{protected:
InfoDialog(const PlayableSetBase& key)
: OwnedPlayableSet(key)
{}
};

class SingleInfoDialog
: public InfoDialog
{public:
SingleInfoDialog(const PlayableSetBase& key)
: InfoDialog(key) // <-- !!!
{}
};

re: Error about inaccessable class

Marcel Müller wrote:It's probably a quirk of the lookup rules, which can be exacerbated by
g++'s inability to interpret them correctly. Try supplying '::', like I
show below.
Try replacing this with

SingleInfoDialog(const ::PlayableSetBase& key)
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

re: Error about inaccessable class

Marcel Müller wrote:There's not just a private base class with that name, but also the name
of that base class is implicitly introduced into the derived class'
scope (it is called "base class name injection"). Class
'PlayableSetBase' is a base class of class 'OwnedPlayableSet', which
means that 'PlayableSetBase' is injected into the 'OwnedPlayableSet'
scope, as if an invisible typedef declaration was there

class OwnedPlayableSet
: public PlayableSetBase
{ public:
...
typedef ::PlayableSetBase PlayableSetBase;
...
};

Now, whenever you use the unqualified 'PlayableSetBase' in any derived
class, it actually refers not to the file-scope name, but to that
class-scope name implicitly declared in 'OwnedPlayableSet'.

In your example, 'InfoDialog' inherits from 'OwnedPlayableSet'
privately, meaning that now 'PlayableSetBase' is private in
'InfoDialog'. And finally, you are trying to access the private
'PlayableSetBase' from 'SingleInfoDialog', which causes the error.

To fix the error, tell the compiler that you want to refer to the global
'PlayableSetBase' name, not the inherited private 'PlayableSetBase' name.

class SingleInfoDialog
: public InfoDialog
{public:
SingleInfoDialog(const ::PlayableSetBase& key)
: InfoDialog(key)
{}
};
--
Best regards,
Andrey Tarasevich

re: Error about inaccessable class

Hi!

Andrey Tarasevich wrote:[...]

Thanks! This was the decisive hint.

I was a bit confused because the error came at the line with the copy
constructor invocation rather that the functions argument list.

That works as expected.

I only wonder a bit why

SingleInfoDialog::SingleInfoDialog(const PlayableSetBase& key) {}

does not give a similar error (assuming a suitable default constructor
of InfoDialog). Types of member function arguments are normally resolved
from within the class scope too.


Marcel