GC: memory collected but destructors not called

[eles via Digitalmars-d]

On Monday, 10 November 2014 at 14:19:26 UTC, Steven Schveighoffer 
wrote:

> Is the resource a GC resource? If so, don't worry about it.

I might be wrong but my view is that in presence of a GC and 
undre the abstraction of R Chen, it is wrong to think about 
memory as being a resource anymore.

If the abstraction is that of a machine with infinite memory, 
then the very mechanism of freeing memory shall be abstracted for.

This asks for decoupling the memory management of the management 
of the other resources and, in particular, RAII-like management.

The management of memory and any other resources is pretty much 
identical under C++ since they share the same paradigm. In GC 
languages, this is no longer the case.

So, the real question (that will also cover destructors throwing 
exceptions and so on) is not what is allowed inside a destructor 
(aka finalizer) but *what is allowed in a constructor* of a 
GC-managed object.

Since for symmetry purposes the destructor should undo what the 
constructor did, this cuts the problem as follows:

  1) in GC-entities, the destructor should not deal with releasing 
memory. Not only this job is no longer his, but *there is no need 
for this kind of job*. Memory is infinite.

  2) from symmetry, the constructor should not allocate memory as 
it would care about its lifetime.

  3) the question in that case is how the other resources are 
managed?

  3a) If they are to be released in the destructor, then the 
destructor's job should be only this (no memory dealloc). In this 
case, the resources should be taken in the constructor.

  3b) if the destructor disappears completely, then the place to 
acquire resources is no longer in the constructor anymore, since 
those will never be released.

  Ideally, a transparent mechanism to allocate memory would be 
needed, without explicit allocation. In this case, the symmetry 
would be conserved: the constructor will only acqire resources 
(but not memory!) and those resources are released, 
symmetrically, in the destructor, at the end of the lifetime.