Re: [Boost-users] [test] Malloc exceptions when using test framework on 64bit OS X 10.6.1

Subject: Re: [Boost-users] [test] Malloc exceptions when using test framework on 64bit OS X 10.6.1
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-09-30 14:48:38

AMDG

Rush Manbert wrote:
> I see your point, but by not using the pointer polymorphically to 
> delete the derived class objects, you now need to write a workaround 
> for how some compilers are implemented. But if the base class 
> destructor were virtual, the delete would be guaranteed to work by the 
> language definition, regardless of the compiler implementation. You 
> wouldn't care how the compiler implemented it, it would just work. And 
> it will still just work as compilers and runtime libraries for C++ 
> evolve. That seems to make more sense to me.

As Gennadiy has already said, the fact that making the destructor
virtual fixes the problem is an artifact of the way that compilers
implement virtual destructors.

with a non virtual destructor, the compiler generates
read the pointer
call the destructor
read the pointer
call operator delete.

The problem is the second read after the destructor has run,

With a virtual destructor the compiler generates
read the pointer
use the v-table to call the destructor/delete.  This is
a single function call so the pointer is only looked up
once.

In Christ,
Steven Watanabe