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WoW:API debugstack (source)

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debugstack([start] [, count1] [, count2])
{{wowapi}}


This function returns a string representation of the current calling stack, similar to the output of the normal Lua debug.traceback() call.<br>
Output a string representation of the current calling stack, similar to the standard Lua debug.traceback() call, which is not present in WoW.


The parameter 'start' is the function level to start the stack trace, which defaults to 1 (the function that called debugstack()).<br>
description = debugstack([thread, ][start[, count1[, count2]]]])
The parameter 'count1' is the number of function calls to show in the first part of the stack trace, which defaults to 12.<br>
The parameter 'count2' is the number of function calls to show in the second part of the stack trace, which defaults to 10.<br>
If there are more than count1+count2 calls in the stack trace, they are separated by "..."<br>


For example, if you had the following call chain:<br>
== Arguments ==
debugstack(2, 1, 3)<br>
=== Parameters ===
a()<br>
:;thread:Thread - a coroutine thread, obtained with coroutine.create(). Use to inspect the current call stack inside a coroutine that has yielded or died.
b()<br>
:;start
c()<br>
:Number - the stack depth at which to start the stack trace (default 1 - the function calling debugstack)
d()<br>
:;count1:Number - the number of functions to output at the top of the stack (default 12)
e()<br>
:;count2:Number - the number of functions to output at the bottom of the stack (default 10)
f()<br>
 
g()<br>
=== Returns ===
(g calls f calls e, etc.)<br>
:;description:String - a multi-line string showing what the current call stack looks like
The output would show b, ..., e, f, g <br>
 
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.
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