A very stupid bug...

[Alf P. Steinbach]

At one point I became convinced that the compiler generated incorrect
destruction code for multiple inheritance.

Oh well.

I finally found it:

virtual ~RawPtrHolder()
{
std::auto_ptr< Type >( myPtr ); // Destroy via std::auto_ptr for access.
}

Uh oh.

Can you see what I did wrogn?


Cheers,

- Alf

 

[cpp4ever]

At one point I became convinced that the compiler generated incorrect
destruction code for multiple inheritance.

Oh well.

I finally found it:

virtual ~RawPtrHolder()
{
std::auto_ptr< Type >( myPtr ); // Destroy via std::auto_ptr for
access.
}

Uh oh.

Can you see what I did wrogn?


Cheers,

- Alf

Tried to free invalid memory because myPtr had not been
reset/initialised to NULL? That would be nasty.

Using std::auto_ptr in a constructor to simplify the throwing
of exceptions, maybe, but I'm not sure I'd ever use std::auto_ptr
like that.

JB

 

[Alf P. Steinbach]

Tried to free invalid memory because myPtr had not been
reset/initialised to NULL? That would be nasty.

Using std::auto_ptr in a constructor to simplify the throwing
of exceptions, maybe, but I'm not sure I'd ever use std::auto_ptr
like that.

Eric J. Holtman had it mostly right (else-thread).

The problem is that the statement is a declaration, of a variable 'myPtr',
instead of constructing a temporary std::auto_ptr instance; it's known as "the
most vexed parse of C++", that anything that syntactically can be treated as a
declaration is treated as a declaration...

My fix was to write

std::auto_ptr<Type>( myPtr+0 )




Cheers,

- Alf

 

[cpp4ever]

Eric J. Holtman had it mostly right (else-thread).

The problem is that the statement is a declaration, of a variable
'myPtr', instead of constructing a temporary std::auto_ptr instance;
it's known as "the most vexed parse of C++", that anything that
syntactically can be treated as a declaration is treated as a
declaration...

My fix was to write

std::auto_ptr<Type>( myPtr+0 )




Cheers,

- Alf

DOH!!! Of course that's the problem. Serves you right for trying to be
too clever by half. I'd have probably declared a temporary variable for
the std::auto_ptr, if only because it's easier to read. Doesn't A.L.F
stand for alien life form?

JB