Re: [Caml-list] Effect of Windows LLP64 architecture on 64 bit MingW OCaml

[Xavier Leroy <Xavier.Leroy@inria.fr>]

On 23/10/15 15:57, Soegtrop, Michael wrote:
> I wonder what differences exist between a 64 bit Linux Ocaml and a 64 bit
> MingW Ocaml. 64bit Windows and MingW64 are what is called LLP64, that is int
> and long are 32 bit and only long long, size_t and pointers are 64 bit as in
> 32 bit Windows. MingW has to follow this convention, otherwise it would be
> incompatible to the Windows headers. But 64 bit Linux tends to be LP64, that
> is int is 32 bit, but long is 64 bit.

That's right.  But the OCaml runtime system abstracts over this
difference, so that you get the same behaviors under Win64 and under
all other 64-bit systems (of the LP64 kind).

> The Ocaml C code doesn’t seem to use
> size abstraction types (like int32, int64)

It does, and even more so in the development version.  The key
abstraction types are "intnat" and "uintnat", designating an integer
type that has the same size as a pointer.  You get those types as
soon as your code includes <caml/mlvalues.h>.

You may have been confused by the use of "long" in the names of the
macros "Val_long" and "Long_val".  Indeed, in the past they used
"long" as "the integer type as big as a pointer type", but since Win64
support was introduced, they actually use type "intnat".

Hope this answers your question.

- Xavier Leroy