mpz_set_si loses long long value on Windows

[Dim XY]

Hello,
I'd like to report a problem with mpz_set_si on Windows 64 (Mingw)

GMP version: 6.1.2
Platform: minw32 on linux ubuntu 18

the program to check:

test-mpz.cpp:

--------------------

#include <stdint.h>

#include <stdio.h>

#include <gmp.h>

int main() {

    mpz_t mpz_a; int64_t a;
    int64_t b = 71000000000;
    mpz_init(mpz_a);
    printf("mpz_a->_mp_size = %d\n",mpz_a->_mp_size);
    mpz_set_si(mpz_a,b);
    printf("mpz_a->_mp_size = %d\n",mpz_a->_mp_size);
    a = mpz_get_si(mpz_a);

    #if defined(_WINDOWS) || defined(_WIN32)
    printf("a=%lli",a);
    #else
    printf("a=%li",a);
    #endif

    return 0;
}

-------------

How to build:

On mingw:

x86_64-w64-mingw32-gcc -I <path-to-mingw32>/x86_64-w64-mingw32/include
libgmp test-mpz.cpp

----------

What's wrong:

On Linux result will be following:

mpz_a->_mp_size = 0
mpz_a->_mp_size = 1
a=71000000000

And on Windows:

mpz_a->_mp_size = 0
mpz_a->_mp_size = -1

a=-2014444032  //  <----- incorrect, lost value!!

-------------

Possible explanation:

mpz_set_si function has the signature:

void mpz_set_si (mpz_ptr dest, signed long int val);

This 'signed long int' type has different sizes of linux (8 bytes) and
windows 64bit (4 bytes) platforms
(https://en.cppreference.com/w/cpp/language/types)

Maybe it is better to use 'long long' type which always has the size
of 8 bytes on any platform?


Kindest

Dmitriy Menshchikov

Komodo platform developer