Minor - P4 https://github.com/mongodb/mongo-c-driver/blob/master/src/mongoc/mongoc-write-command.c#L511
BSON_ASSERT (max_bson_size);
/* max BSON object size + 16k - 2 bytes for ending NUL bytes.
* server guarantees there is enough room: SERVER-10643
*/
int32_t max_cmd_size = max_bson_size + 16382;
Statement followed by variable dec in the same scope is not permitted in C89 (only affects compilations with a meaningful BSON_ASSERT, e.g DEBUG)
(this appears to be the only instance in the code base)