If you have a string held in not-guaranteed-null-terminated storage, you cannot currently use that string directly to search within a bson_t with bson_iter_find or bson_iter_init_find, and instead must heap allocate a known-to-be-null-terminated temporary string to pass in.

The C++ driver stopped using bson_iter_init_find in CXX-992 to avoid the overhead of this temporary allocation, and began walking and comparing keys directly. Unfortunately, the implementation was buggy, leading to CXX-1476.

If the two forms of find had overloads that took an associated length for the key, then the C++ driver could use those rather than re-implementing key comparison itself.

If this is not viable for some reason, an alternative would be to make an overload of bson_iter_key that returned the key length in an out parameter. This would allow the C++ driver to avoid a required (though currently not present) call to strlen on the result of bson_iter_key, which is almost certainly redundant work to recover information that the C driver has already determined.

It may make sense to implement the length returning form of bson_iter_key even if the bson_iter_find changes are made anyway, as searching in BSON is very common, and the C driver should surface all information available that may assist clients.