Re: [Caml-list] Re: Closure marshalling inconsistency

[rossberg@mpi-sws.org]

Oleg wrote:
>
> Lauri Alanko wrote:
>> Marshalling closures with references to globals is precarious
>> business.
>
> Indeed. I would not blame OCaml though: OCaml serialization functions
> (when invoked with the right flags) ensure the preservation of sharing
> of components _within_ a serialized value. There are no guarantees
> about the preservation of sharing _between_ separately serialized
> values. The documentation explicitly says so: ``Sharing between values
> marshaled by successive calls to Marshal.to_channel is not detected,
> though.''  That is, if v1 and v2 share a component, the results of
> pickling/unpickling v1 and separately v2 may not share the component.

True, but I think Lauri complains about a slightly different issue, namely
sharing inconsistencies between a _single_ marshalled value and the program
environment. Or in other words, that the language does not actually define
what it means to be "_within_ a serialized values", nor implements it
consistently.

There are obvious ways in which this could be made coherent, but they are
likely to be difficult to implement as an afterthought.

> I might agree that this is a bug -- but not that it is a bug in
> OCaml. I might agree with the argument that it is a global mutable
> variable that is the bug, in programmer's code.

He he. That sounds like an entirely un-MLish kind of argument. The language
has undefined and incoherent semantics? Of course, it's the programmer's
mistake to expect otherwise! ;)

/Andreas