debug.getregistry () Returns the registry table (see §4.5).

debug.getupvalue (f, up) This function returns the name and the value of the upvalue with index up of the function f. The function returns nil if there is no upvalue with the given index. Variable names starting with '(' (open parenthesis) represent variables with no known names (variables from chunks saved without debug information).

debug.getuservalue (u) Returns the Lua value associated to u. If u is not a full userdata, returns nil.

debug.sethook ([thread,] hook, mask [, count]) Sets the given function as a hook. The string mask and the number count describe when the hook will be called. The string mask may have any combination of the following characters, with the given meaning: 'c': the hook is called every time Lua calls a function; 'r': the hook is called every time Lua returns from a function; 'l': the hook is called every time Lua enters a new line of code. Moreover, with a count different from zero, the

debug.setlocal ([thread,] level, local, value) This function assigns the value value to the local variable with index local of the function at level level of the stack. The function returns nil if there is no local variable with the given index, and raises an error when called with a level out of range. (You can call getinfo to check whether the level is valid.) Otherwise, it returns the name of the local variable. See debug.getlocal for more information about variable indices and names.

debug.setmetatable (value, table) Sets the metatable for the given value to the given table (which can be nil). Returns value.

debug.setupvalue (f, up, value) This function assigns the value value to the upvalue with index up of the function f. The function returns nil if there is no upvalue with the given index. Otherwise, it returns the name of the upvalue.

debug.setuservalue (udata, value) Sets the given value as the Lua value associated to the given udata. udata must be a full userdata. Returns udata.

debug.traceback ([thread,] [message [, level]]) If message is present but is neither a string nor nil, this function returns message without further processing. Otherwise, it returns a string with a traceback of the call stack. The optional message string is appended at the beginning of the traceback. An optional level number tells at which level to start the traceback (default is 1, the function calling traceback).

debug.upvalueid (f, n) Returns a unique identifier (as a light userdata) for the upvalue numbered n from the given function. These unique identifiers allow a program to check whether different closures share upvalues. Lua closures that share an upvalue (that is, that access a same external local variable) will return identical ids for those upvalue indices.