what is the length of a long (motivated by GSL2.1 and GSLL)

[Mirko Vukovic]

This message has two audiences:  One the general CFFI group, and second the
GSL maintainer.

This is using latest CCL and SBCL on 64-bit Windows 7, and MSYS2 running
64-bit MinGW and its GSL2.0 and 2.1.

Running GSL 2.0 and 2.1 under GSLL resulted in exception violations.  I
could eliminate them by specifying the length of an integer as 8 instead of
4 bytes.

My question has to do with the origin of this specification, since it is
derived from CFFI and GSLL, not hard-coded.

Specifically, in GSLL, the following code in init/types.lisp:
(case (cffi:foreign-type-size :long)
  *(8 (push :int64 *features*))*
  *(4 (push :int32 *features*))*)

evaluates to 4, pushing :int32 into *features*.  Here is some additional
output of cffi:foreign-type-size on my machine:

GSL> (cffi:foreign-type-size :double)
8
GSL> (cffi:foreign-type-size :long)
4
GSL> (cffi:foreign-type-size :long-long)
8
GSL> (cffi:foreign-type-size :int)
4

This feature eventually makes its way to other code in GSLL.  In the Linear
Algebra module, the function make-permutation (in data/permutation.lisp)
has this line:
(make-instance
 'permutation
 :element-type '(unsigned-byte *#+int64 64* *#+int32 32*)
 :dimensions (if (typep n 'permutation) (grid:dimensions n) (list n)))))

In my environment element type resulted in unsigned-byte 32.

When I hard-coded my features to :int64 (and unsigned-byte 64), all the
exception errors disappeared.

I hope this gives enough background to fix this error (either in my setup,
gsll, or cffi).

Thanks,

Mirko
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