Hi Joris,
It might be worth us including a 64 bit C++ constructor for mpz's on
Windows 64. At the moment the constructor basically mimics mpz_set_ui,
which explains the limitation.
Brian may be able to let us know whether it is even possible to do
this (I don't know enough C++ to say for sure).
Bill.
On 24 October 2011 15:58, Joris Mooij <joris.mo...@gmail.com> wrote:
> Hi,
>
> first of all, I would like to thank the developers of (GMP and) MPIR
> for this great library. I am using it in my own open source library,
> libDAI.
>
> When using MPIR in a Win64 environment, I encountered the problem that
> the C++ wrappers do not seem to handle 64-bit integers, like size_t's
> (or long long ints). This is illustrated by the following code, which
> compiles fine under 64-bit linux, but fails to compile in a Windows 64
> environment:
>
> ---
> #include <gmpxx.h>
> #include <iostream>
> using namespace std;
> int main(void) {
> size_t a = 5;
> mpz_class b(a);
> cout << b.get_ui() << endl;
> return 0;
> }
> ---
>
> The reason seems to be that a size_t is a 64-bit integer in Win64,
> whereas an unsigned long is only 32 bits in that environment, and the C
> ++ wrapper classes in MPIR only provide a constructor for mpz_class
> from (up to) 32-bit integer types. The C part of the library does
> provide such functionality by the function mpz_init_set_ux().
> On 64-bit linux, however, an unsigned long is 64 bits, and therefore
> the code runs fine.
>
> Now to me, this seems to be an undesirable cross-platform
> incompatability. On the MPIR homepage, I read that two of the primary
> goals of MPIR are:
> - To maintain full interface support with GMP - MPIR is a drop-in
> replacement for GMP.
> - Support for building MPIR using Microsoft Visual Studio 2010 for use
> in both 32-bit and 64-bit versions of Windows.
> Such a platform dependence as discussed above seems to conflict with
> these goals.
>
> So I have the following questions (sorry, I am new to this list, and
> didn't read all the previous conversations, although I tried searching
> for this issue on this list, without much success):
> - Is this a known issue (I saw some other posts on this list and on
> the internet which mention, so I suspect the answer would be "yes")?
> - Is somebody working on it?
> - Would it be difficult to add support for 64-bit integers to the C++
> wrappers also for platforms where an unsigned long is only 32 bits?
> - Is there a reason that this hasn't been dealt with yet?
>
> Thanks for your time,
> Joris
>
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