Multiple inheritance and destructors

[Christopher Benson-Manica]

Okay, having purchased the excellent Josuttis book last night, I've
almost got my little streambuf subclass bit worked out. Now, though,
I'm faced with some issues with the destructors...

public TRFileStream : public TLSFile, public std::streambuf
{
...
};

The problem, I think, is that ~TLSFile is *not* virtual, but
~std::streambuf is. How can I reconcile these two destructors?

 

[John Harrison]

Okay, having purchased the excellent Josuttis book last night, I've
almost got my little streambuf subclass bit worked out. Now, though,
I'm faced with some issues with the destructors...

public TRFileStream : public TLSFile, public std::streambuf
{
...
};

The problem, I think, is that ~TLSFile is *not* virtual, but
~std::streambuf is. How can I reconcile these two destructors?

Not sure there is a problem with that. What problem are you actually seeing?

john

 

[Christopher Benson-Manica]

Not sure there is a problem with that. What problem are you actually seeing?

Well, with no destructor declared in the function, I'm told

Virtual function '_fastcall TWFileStream::~TWFileStream()' conflicts with base
class 'streambuf'

(note the Borland-specific __fastcall qualifier, which I perhaps
unwisely did not mention in my original post)

I get the same error if I attempt to specify a destructor like this:

__fastcall ~TWFileStream() {;} //or, alternatively
virtual __fastcall ~TWFileStream() {;}

And if I specify it thus (in an attempt to placate std::streambuf):

virtual ~TWFileStream() {;}

Virtual function 'TWFileStream::~TWFileStream()' conflicts with base class
'TLSFile'

Is this stupid Borland qualifier going to ruin what could otherwise be
a wonderful piece of code? I'd appreciate any ideas...

 

[John Harrison]

seeing?

Well, with no destructor declared in the function, I'm told

Virtual function '_fastcall TWFileStream::~TWFileStream()' conflicts with base
class 'streambuf'

(note the Borland-specific __fastcall qualifier, which I perhaps
unwisely did not mention in my original post)

I get the same error if I attempt to specify a destructor like this:

__fastcall ~TWFileStream() {;} //or, alternatively
virtual __fastcall ~TWFileStream() {;}

And if I specify it thus (in an attempt to placate std::streambuf):

virtual ~TWFileStream() {;}

Virtual function 'TWFileStream::~TWFileStream()' conflicts with base class
'TLSFile'

Is this stupid Borland qualifier going to ruin what could otherwise be
a wonderful piece of code? I'd appreciate any ideas...

Well I have no idea about the Borland bit (ask on a Borland newsgroup,
details from their community web page)but since TLSFile doesn't seem to have
been designed for inheritance perhaps you could recode

class TWFileStream : public std::streambuf
{
...
private:
TLSFile m_file;
};

Tedious since you'll have to wrap the entire TLSFile interface, but maybe
it'll work.

john