There is nothing that forbids doing that, to my knowledge (do so the same way
you would call other libc functions). But remember to check for ENOMEM/NULL
(and eventually free it).
Something to keep in mind though (not specific to malloc): if you put the
pointer in some object, and the record type of that object has a record
printer, and that record printer dereferences the pointer, then when the object
is printed after deallocation, you (almost tautologically) have use-after-free,
and before initialisation you have another problem.
While obvious, this can happen in unexpected situations. Consider:
;; ENOMEM / NULL handling omitted.
;; assume that the record printer, when the pointer field isn’t #false,
;; dereferences the pointer and prints something about it.
;; (if it doesn’t check for #false, you also have problems, but different
problems)
(define (allocate-thing)
(let ((r (make-record-thingie))
(p (malloc-something)))
;; even if setting the field is integrated in the constructor,
;; then internally Guile will split the allocation and setting the fields
;; (although, different than C, it is still initialised after allocation, to
#false IIRC)
(set-some-field! r p)
(do-some-initialisation! r)
r))
,trace (allocate-thing)
Because ‘trace’ looks at each procedure call (including
do-some-initialisation!) inside and prints the argument, you end up with use
before initialisation (a variant with use-after-free can also be written).
(For a non-malloc example, see the bug report (+ patch) about GOOPS methods and
,trace.)
Best regards,
Maxime Devos
