This error seems wrong:
#lang racket
(require ffi/unsafe
ffi/unsafe/cvector)
(define-cstruct _mpz ([alloc _int]
[size _int]
[limbs (_gcable _cvector)]))
(define z (make-mpz 1 1 (list->cvector '(1) _long)))
(mpz-limbs z)
>>> _cvector: cannot automatically convert a C pointer to a cvector
The error might be correct, though late and confusing, if a cvector's
"base representation" isn't a pointer type. Is it?
If that error is correct, then how are FFI users meant to define a C
struct that has a "long *" field that points to an array? I've not yet
managed to define one whose instances survive a garbage collection cycle
without using (_gcable _cvector). Here's one of my desperate attempts:
#lang racket
(require ffi/unsafe
ffi/unsafe/cvector)
(define-cstruct _mpz ([alloc _int] [size _int] [limbs _gcpointer]))
(define z (make-mpz 1 1 (cvector-ptr (list->cvector '(1) _long))))
> (ptr-ref (mpz-limbs z) _long 0)
1
> (collect-garbage)
> (ptr-ref (mpz-limbs z) _long 0)
139856348920568
I mean to be complain-y this time. This shouldn't be this hard to figure
out.
Neil ⊥
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