WoW API: debugstack

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← WoW API < debugstack

Output a string representation of the current calling stack, similar to the standard Lua debug.traceback() call, which is not present in WoW.

description = debugstack([thread, ][start[, count1[, count2]]]])

Arguments

Parameters

thread

Thread - a coroutine thread, obtained with coroutine.create(). Use to inspect the current call stack inside a coroutine that has yielded or died.

start

Number - the stack depth at which to start the stack trace (default 1 - the function calling debugstack)

count1

Number - the number of functions to output at the top of the stack (default 12)

count2

Number - the number of functions to output at the bottom of the stack (default 10)

Returns

description

String - a multi-line string showing what the current call stack looks like

If there are more than count1+count2 calls in the stack, they are separated by a "..." line.

Example

Assume the following example file, "file.lua":

 1: function a()
 2:   error("Boom!"); 
 3: end
 4:
 5: function b() a(); end
 6:
 7: function c() b(); end
 8:
 9: function d() c(); end
10:
11: function e() d(); end
12:
13: function f() e(); end
14:
15: function errhandler(msg)
16:   print (msg .. "\nCall stack: \n" .. debugstack(2, 3, 2));
17: end
18:
19: xpcall(f, errhandler);

This would output something along the following:

file.lua:2: Boom!
Call stack:
file.lua:2: in function a
file.lua:5: in function b
file.lua:7: in function c
...
file.lua:13: in function f
file.lua:19
 

Example 2

Combining debugstack with a strmatch can enable you to get the current line of a function call.

 1: function debugprint(msg)
 2:   local line = strmatch(debugstack(2),":(%d):");
 3:   print("Debug Print on Line "..line.." with message: "..msg);
 4: end
 5:
 6: function doSomething()
 7:   debugprint("We tried to do something.");
 8: end

This would return the following output from print:

Debug Print on Line 7 with message: We tried to do something.

Example 3

Using debugstack to find out the location of an error in a coroutine.

 1: function f()
 2:   print ("a">0)  -- this will cause an error
 3: end
 4:
 5: thread = coroutine.create(f)
 6: executed_ok,message = coroutine.resume(thread)
 7:
 8: if not executed_ok then
 9:   print("Error: "..message.." in "..debugstack(thread))
10: end

Note that despite its all-lowercase name, this is not a core Lua function. It is a WoW API.