[c++] gcnew and new

 

http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/a10e4f13-6167-4f1a-bba6-c6010cdf6f89

The new and gcnew operator are similar. Both allocate memory and invoke the constructor of the object. Whereas new allocates memory from a native heap and returns a pointer, gcnew will allocate memory from the GC heap and return a handle. A boxed value type is easy to recognize, as the type is simply a handle to value type. For example:

      int m = 42;             // integer on the stack
      int* n = new int(42);   // integer on a native heap
      int^ o = gcnew int(42); // boxed integer on the GC heap

There are other ways to create boxed value types, but I will leave that for another time when I discuss the implementation of boxed value types.

Why is it important to distinguish whether an instance of an object is on the GC heap or a native heap? The GC algorithm implemented by the CLR is a generational compacting garbage collector. This means that the memory location of the object can change upon each garbage collection. This does not happen on the native heap. A pointer refers to an instance in memory that never moves. The garbage collector ensures that a handle always points to the right instance.