Re: Interfacing to C and long long data type

[Keith Thompson <kst-u@mib.org>]

Maciej Sobczak <see.my.homepage@gmail.com> writes:
> C has a long long data type, which is supposed to be at least as big
> as long. Recently, the same data type is being added to C++ as well
> (they were working on it for a long long time).

In addition, long long is required to be at least 64 bits wide (long
is required to be at least 32 bits wide).

> The problem is that there is no corresponding type in Interfaces.C.
> 
> Is it possible to interface with C APIs that use long long?

You can declare

    type C_Long_Long is range -2**63 .. 2**63-1;

It's not guaranteed to match C's long long, but I've never heard of a
C implementation where long long is anything other than exactly 64
bits.

There's also "unsigned long long", which you can declare in Ada as:

    type C_Unsigned_Long_Long is mod 2**64;

Note that "long long" and "unsigned long long" were introduced in the
1999 ISO C standard, which is fully implemented by only a handful of C
compilers.  Many pre-C99 compilers support "long long" as an
extension, but there are still some that don't.

> Similar issue exists with long long double.

Not really, because there is no "long long double" type in C or C++.
There's "long double", but that's been in C since at least the 1989
standard, and I presume there's already a corresponding type in
Interfaces.C.  (C and C++ have 3 floating-point types: "float",
"double", and "long double".)

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Nokia
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