crypto_sign_ed25519_BYTES
uint8_t sig[crypto_sign_ed25519_BYTES + sizeof(signbuf)];
if (len > crypto_sign_ed25519_BYTES) {
datalen >= INT_MAX - crypto_sign_ed25519_BYTES)
smlen = slen = datalen + crypto_sign_ed25519_BYTES;
dlen >= INT_MAX - crypto_sign_ed25519_BYTES ||
if (len > crypto_sign_ed25519_BYTES) {