ERR_load_strings() registers error strings for library number lib.str is an array of error string data:
typedef struct ERR_string_data_st
{
unsigned long error;
char *string;
} ERR_STRING_DATA;
The error code is generated from the library number and a function and reason code: error = ERR_PACK(lib, func, reason). ERR_PACK() is a macro.
The last entry in the array is {0,0}.
ERR_get_next_error_library() can be used to assign library numbers to user libraries at runtime.