* libguile/vectors.c (scm_vector_length, scm_c_vector_length):
(scm_c_vector_ref, scm_c_vector_set_x): Deprecate the use of these
procedures on weak vectors.
* test-suite/tests/guardians.test:
* test-suite/tests/weaks.test: Adapt test suites.
* test-suite/tests/weaks.test: Add tests.
* libguile/hashtab.c (scm_hash_fn_set_x): Fix updates to weak-value hash
tables to not deadlock inside the alloc lock.
* libguile/hashtab.c (struct t_assoc_args, do_weak_bucket_assoc):
Remove.
(struct t_fixup_args): New type.
(do_weak_bucket_fixup): New function.
(weak_bucket_assoc): Use it. Keep strong references to BUCKET's
entries in STRONG_REFS. Call ASSOC once the alloc lock has been
released. This fixes bug #29616.
* test-suite/tests/weaks.test ("assoc can do anything"): New test.
* test-suite/tests/weaks.test: Enclose in a module.
(valid?): New procedure.
("weak-hash")["weak-key dies, "weak-value dies", "double-weak dies"]:
Check that all the values are `valid?', in addition to checking that
at least one of them is #f.
* libguile/hashtab.c (scm_hash_fn_set_x): Register a disappearing link
to VAL when TABLE is weak-value.
* test-suite/tests/weaks.test ("weak-hash")["weak-key dies", "weak-value
dies", "doubly-weak dies"]: Use `hash-set!' and `hash-ref', not
`hashq-set!' and `hashq-ref', otherwise these tests would always
succeed because (eq? "this" "this") => #f.
["lives"]: Use `hash-ref' and `hash-set!' too for consistency.
