int X509_PURPOSE_add(int id, int trust, int flags,
                     int (*ck) (const X509_PURPOSE *, const X509 *, int),
                     const char *name, const char *sname, void *arg)
{
    int idx;
    X509_PURPOSE *ptmp;
    /*
     * This is set according to what we change: application can't set it
     */
    flags &= ~X509_PURPOSE_DYNAMIC;
    /* This will always be set for application modified trust entries */
    flags |= X509_PURPOSE_DYNAMIC_NAME;
    /* Get existing entry if any */
    idx = X509_PURPOSE_get_by_id(id);
    /* Need a new entry */
    if (idx == -1) {
        if ((ptmp = OPENSSL_malloc(sizeof(*ptmp))) == NULL) {
            X509V3err(X509V3_F_X509_PURPOSE_ADD, ERR_R_MALLOC_FAILURE);
            return 0;
        }
        ptmp->flags = X509_PURPOSE_DYNAMIC;
    } else
        ptmp = X509_PURPOSE_get0(idx);

    /* OPENSSL_free existing name if dynamic */
    if (ptmp->flags & X509_PURPOSE_DYNAMIC_NAME) {
        OPENSSL_free(ptmp->name);
        OPENSSL_free(ptmp->sname);
    }
    /* dup supplied name */
    ptmp->name = OPENSSL_strdup(name);
    ptmp->sname = OPENSSL_strdup(sname);
    if (!ptmp->name || !ptmp->sname) {
        X509V3err(X509V3_F_X509_PURPOSE_ADD, ERR_R_MALLOC_FAILURE);
        goto err;
    }
    /* Keep the dynamic flag of existing entry */
    ptmp->flags &= X509_PURPOSE_DYNAMIC;
    /* Set all other flags */
    ptmp->flags |= flags;

    ptmp->purpose = id;
    ptmp->trust = trust;
    ptmp->check_purpose = ck;
    ptmp->usr_data = arg;

    /* If its a new entry manage the dynamic table */
    if (idx == -1) {
        if (xptable == NULL
            && (xptable = sk_X509_PURPOSE_new(xp_cmp)) == NULL) {
            X509V3err(X509V3_F_X509_PURPOSE_ADD, ERR_R_MALLOC_FAILURE);
            goto err;
        }
        if (!sk_X509_PURPOSE_push(xptable, ptmp)) {
            X509V3err(X509V3_F_X509_PURPOSE_ADD, ERR_R_MALLOC_FAILURE);
            goto err;
        }
    }
    return 1;
 err:
    if (idx == -1) {
        OPENSSL_free(ptmp->name);
        OPENSSL_free(ptmp->sname);
        OPENSSL_free(ptmp);
    }
    return 0;
}