"Jeroen Mostert" wrote:

> john conwell wrote:
> > I'm using Marshal::StructureToPtr to well...marshal a struct over to
> > unmanaged memory and get its pointer.
> >
> > Which method should I use to destroy the memory the pointer represents?
>
> Because Marshal.StructureToPtr() requires already allocated memory, you
> should use the counterpart of whatever method you used to allocate it. If
> it's statically allocated, don't free it. If you used GlobalAlloc(), use
> GlobalFree(). If new[], use delete, if Marshal.AllocHGlobal(), use
> Marshal.FreeHGlobal(), if Marshal.AllocCoTaskMem() use
> Marshal.FreeCoTaskMem(), etc.
>
> > Marshal.DestroyStructure or Marshal.FreehGlobal? Does it matter?
> >
> They have completely different goals. Marshal.DestroyStructure() is for
> freeing memory allocated by reference fields of the struct. In particular,
> it calls SysFreeString() for any string fields marshalled as BSTR, since
> separate memory needs to be allocated for them that must be freed before the
> structure itself is freed.
>
> If you have such fields, you need to call .DestroyStructure() before freeing
> the struct itself. You can do that with .FreeHGlobal(), if the memory was
> allocated with .AllocHGlobal().
>
> --
> J.