OpenSSL::X509::Store#verify_callback=

static VALUE
ossl_x509store_set_vfy_cb(VALUE self, VALUE cb)
{
    X509_STORE *store;

    GetX509Store(self, store);
    rb_iv_set(self, "@verify_callback", cb);
    // We don't need to trigger a write barrier because `rb_iv_set` did it.
    X509_STORE_set_ex_data(store, store_ex_verify_cb_idx, (void *)cb);

    return cb;
}