I think the size of this array must be set with realloc. If two consecutive nodes are hidden, in fact, one does not need to store both their hases, they can directly store the root hash of the subtree.

[FDeRubeis]

nss-tlsn/nss/lib/ssl/tlsproof.c

Line 1095 in 5730a7a

rpi->proof_merkle_hashes = allocate_string_array(rpi->hash_size, rpi->num_hidden_chunks);