Maybe documentation issue: std::size_t is unsigned, but start_object is supposed to pass -1 ?

[mj-64]

The doc for the SAX interface states:

// called when an object or array begins or ends, resp. The number of elements is passed (or -1 if not known)
bool start_object(std::size_t elements);
bool end_object();
bool start_array(std::size_t elements);
bool end_array();

std::size_t is an unsigned type, so it cannot be -1. Should that read as -1 = 0xffffffff aka std::numeric_limits<std::size_t>::max() ?

[gregmarr]

It's just that value cast to that type, or std::size_t(-1).

[nlohmann]

Exactly.