#define BSON_APPEND_UNDEFINED(b, key) \

       MongoDB, Inc

       2009-present, MongoDB, Inc.

1.30.4                                            Jun 08, 2025                          BSON_APPEND_UNDEFINED(3)

       The  bson_append_undefined()  function  shall  append  a new element to bson of type BSON_TYPE_UNDEFINED.
       Undefined is common in Javascript. However, this element type is deprecated and should not be used in new
       code.

       • bson: A bson_t.

       • key: An ASCII C string containing the name of the field.

       • key_length: The length of key in bytes, or -1 to determine the length with strlen().

       Returns true if the operation was applied successfully. The function will fail  if  appending  the  value
       grows bson larger than INT32_MAX.

          #define BSON_APPEND_UNDEFINED(b, key) \
             bson_append_undefined (b, key, (int) strlen (key))

          bool
          bson_append_undefined (bson_t *bson, const char *key, int key_length);