DH_get_length
long l = DH_get_length(dh);
dupkey->length = DH_get_length(dh);
long l = DH_get_length(dh);
OSSL_DEPRECATEDIN_3_0 long DH_get_length(const DH *dh);
length = DH_get_length(dh);
if (!TEST_int_eq((int)DH_get_length(dh), 0))