Re: using delete expression on global operator new allocated memory

From:
"Alf P. Steinbach" <alfps@start.no>
Newsgroups:
comp.lang.c++
Date:
Wed, 30 Apr 2008 16:02:19 +0200
Message-ID:
<HLOdnU2ZZ-1w5oXVnZ2dnUVZ_rzinZ2d@comnet>
* dizzy:

Hi

I wonder if this code is standard conformant and should work on all
conformant implementations (for some type T):

1: void* mem = ::operator new(sizeof(T));
2: T* p = new(mem) T(args...);
3: delete p;

line 2 I know it should be fine because global operator new should return
memory aligned for any type. The thing I wonder about is line 3. Should
this always work?

PS: the code might seem silly, it is needed because I need to decouple the
point of storage type used (which on 2 different codepaths can be on stack
or dynamic) from the point of actual initialization of the object and its
arguments (thus I need to use placement new); another solution I am aware
of whould be using some kind of "factory functors" (like the ones in boost)
but that would require for me to use template functions which is what I
want to avoid in the first place


Yes, the code is silly.

Stack (or in C++ terminology local variable):

   int main()
   {
      T o( args... );
   }

Dynamic:

   int main()
   {
       std::auto_ptr<T> p( new T( args... ) );
   }

Cheers, & hth.,

- Alf

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