wanted: EQUALP/EQUAL/EQL for SAPs

[3b]

CFFI uses SB-SYS:INT-SAPs as foreign pointers on sbcl, but since SAPs can't be compared with with EQ/EQL/EQUAL/EQUALP, they can't be used as keys in a hash table without using a non-portable test, or extracting the pointer value by hand and using that as a key.

test cases:
(let ((h (make-hash-table :test 'equalp)))
  (setf (gethash (cffi:make-pointer 12345) h) 123)
  (gethash (cffi:make-pointer 12345) h))

expected 123,T
actual results NIL,NIL, on sbcl 1.0.43.78 linux x86-64

Works on CCL, using EQL, EQUAL and EQUALP

There was some related discussion on #sbcl (~18:50 in http://ccl.clozure.com/irc-logs/sbcl/2010-09/sbcl-2010.09.19.txt), but nothing was decided.

[Nikodemus Siivola (nikodemus)]

I suspect SAPs could very well be EQL-comparable since they are immutable.

Though I think I was opposed to EQLness in that discussion, or at least sceptical, on reflection EQL comparison does sound right "numberlike immutable objects" -- but I'm still on the fence re. extending a very primitive standard operator.

However, re: CFFI, pointers, and hash-tables: I believe the portable solution is to use CFFI:POINTER-ADDRESS as the key.