are APIs for querying the type, manipulating the reference count, and
for constructing and manipulating values of different types.
+Unless noted otherwise, all API functions return an error value if an
+error occurs. Depending on the function's signature, the error value
+is either *NULL* or -1. Invalid arguments or invalid input are
+apparent sources for errors. Memory allocation and I/O operations may
+also cause errors.
+
Type
----
.. cfunction:: int json_typeof(const json_t *json)
Return the type of the JSON value (a :ctype:`json_type` cast to
- :ctype:`int`). This function is actually implemented as a macro for
- speed.
+ :ctype:`int`). *json* MUST NOT be *NULL*. This function is actually
+ implemented as a macro for speed.
.. cfunction:: json_is_object(const json_t *json)
json_is_array(const json_t *json)