fd38da9e__Writing_Multithreaded_Clients__Description
[Field] *ltf_get_errno [Description] 
Function pointer for getting the value of the errno variable. This function is called by the client when needed if the function pointer is not NULL. In a threaded environment, errno is typically redefined so that it has a value for each thread, rather than a global value for the entire process. This redefinition is done at compile time. Because the libldap library does not know what method your code and threading environment will use to get the value of errno for each thread, it calls this function to return the value of errno.
Mozilla LDAP C SDK: Chapter 16 - Writing Multithreaded Clients
Description