Constructor taking 64-bit integer missing on (some) Windows C++ compilers

[Vincent Lefevre]

On 2020-06-06 14:28:21 +1000, Mihai Preda wrote:
> I'm using libgmp-dev 6.1.2 on Ubuntu myself, but the bug report
> concerns an unspecified version of GMP on Windows. I have reasons to
> suspect the bug is valid for the most recent GMP. Clear cause analysis
> and proposed solution is included.
> 
> I'm not a Windows user myself. I develop an open-source app that users
> are compiling, among others, on Windows with mingw or other c++
> compilers on windows. A common habit of these c++ compilers on windows
> is to have 32-bit long.

There's the same issue with 32-bit architectures, whatever the OS.

> In my app I construct a mpz_class from a 64-bit unsigned integer, like this:
> uint64_t h = ...;
> mpz_class{h};
> 
> At this point the C++ compiler on windows (where long is 32-bit)
> reports errors, see at the end. The problem is that the set of
> constructors does not include one taking a 64-bit integer:
> 
> #define __GMPXX_DEFINE_ARITHMETIC_CONSTRUCTORS        \
>   __gmp_expr(signed char c) { init_si(c); }        \
>   __gmp_expr(unsigned char c) { init_ui(c); }        \
>   __gmp_expr(signed int i) { init_si(i); }        \
>   __gmp_expr(unsigned int i) { init_ui(i); }        \
>   __gmp_expr(signed short int s) { init_si(s); }    \
>   __gmp_expr(unsigned short int s) { init_ui(s); }    \
>   __gmp_expr(signed long int l) { init_si(l); }        \
>   __gmp_expr(unsigned long int l) { init_ui(l); }    \
>   __gmp_expr(float f) { init_d(f); }            \
>   __gmp_expr(double d) { init_d(d); }
> 
> Among all in the list above, none takes a uint64_t or int64_t.
> 
> The fix could consist in having these constructors take int64_t
> instead of long int, etc. I.e. take explicitly-sized typed instead of
> the "long" which is variable-size.

I would rather suggest to support intmax_t and uintmax_t.

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