Better argument validation

[jansson.git] / doc / apiref.rst

diff --git a/doc/apiref.rst b/doc/apiref.rst
index c70c0bc..ea38343 100644 (file)
--- a/doc/apiref.rst
+++ b/doc/apiref.rst
@@ -41,6 +41,12 @@ Objects of :ctype:`json_t` are always used through a pointer. There
 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
 ----
@@ -80,8 +86,8 @@ functions:
 .. 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)
@@ -121,7 +127,7 @@ The following functions are used to manipulate the reference count.
 
 .. cfunction:: json_t *json_incref(json_t *json)
 
-   Increment the reference count of *json*.
+   Increment the reference count of *json*. Returns *json*.
 
 .. cfunction:: void json_decref(json_t *json)
 
@@ -304,9 +310,9 @@ Unicode string and the value is any JSON value.
 .. cfunction:: int json_object_set(json_t *object, const char *key, json_t *value)
 
    Set the value of *key* to *value* in *object*. *key* must be a
-   valid terminated UTF-8 encoded Unicode string. If there already is
-   a value for *key*, it is replaced by the new value. Returns 0 on
-   success and -1 on error.
+   valid null terminated UTF-8 encoded Unicode string. If there
+   already is a value for *key*, it is replaced by the new value.
+   Returns 0 on success and -1 on error.
 
 .. cfunction:: int json_object_set_new(json_t *object, const char *key, json_t *value)