Graal Forums - Introducing Callstack Access

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- - Introducing Callstack Access (https://forums.graalonline.com/forums/showthread.php?t=78280)

Introducing Callstack Access

Introduction

This is possibly my most wanted feature in GScript for some time: callstack access.

Callstack access allows you to see which objects and functions are calling other objects or functions. This means you can add better script security by, say, checking which NPCs are trying to call your bank functions, for example. It also can be used for script debugging.

Does it work on all servers yet? Probably not. Try it, and if it doesn't work, you can request your NPC-Server to be updated with it. :)

How callstack access works

First, let's examine how to get the contents of the callstack.

The getCallStack() function returns an array of links. The array that getCallStack() returns is a chronological list of the function call chain.

The important thing to recognise about these links is that they are not direct links to the calling function or NPC themselves, but instead they are an object linking to the temp. scope of the calling functions. Yes, this means that you can access temp. variables of functions earlier in the call chain. (See section below)

There is also a sub-object named "scriptcallobject", which is a link to the object that is calling the function.

Finally, there is another variable called "name" which returns the name of the calling function.

Code Example

Now, just to make the example a bit more straight-forward, we'll demonstrate this with just two NPCs; TestNPC, and TestNPC2.

Here is the code in TestNPC:

PHP Code:


		
			
function onCreated()

{

  this.testCallStack();

}



public function testCallStack()

{

  temp.callstack = getCallStack();



  for (temp.i = temp.callstack.size() - 1; temp.i >= 0; temp.i --)

  {

    echo("call stack entry " @ temp.i @ ": " @ 

      temp.callstack[temp.i].scriptcallobject.name @ "." @ temp.callstack[temp.i].name);

  }

}

(You'll notice that the for (temp.foo: bar) iterator is not used here, or otherwise you might overwrite temp variables.)

And then TestNPC2:

PHP Code:


		
			
function onCreated()

{

  TestNPC.testCallStack();

}

Updating the script of TestNPC will reveal this in RC:

Quote:

call stack entry 1: TestNPC.testCallStack
call stack entry 0: TestNPC.onCreated

Updating TestNPC2 instead reveals this:

Quote:

call stack entry 1: TestNPC.testCallStack
call stack entry 0: TestNPC.onCreated

This shows the order in which functions have been called in order to reach the current function.

Accessing temp variables

Instead of using scriptcallobject, you can access temp names directly, i.e.:

PHP Code:


		
			
function onCreated()

{

  temp.foo = "two";

  

  this.testCallStack();

}



public function testCallStack()

{

  temp.foo = "one";

  temp.callstack = getCallStack();



  for (temp.i = temp.callstack.size() - 1; temp.i >= 0; temp.i --)

  {

    echo("variable contents " @ temp.callstack[temp.i].foo);

  }

}

Upon updating the script, this will appear in RC:

Quote:

variable contents one
variable contents two

A wicked way to secure scripts from pesky staff ^^. Although I wanted protected variables, this will definitely help ^^ <3 for Stefan!

Bank DBNPC

PHP Code:


		
			
public function deposit()

{

  temp.stack = getCallStack();

  

  if (temp.stack[0].scriptcallobject.name != "Twinny/Test") //Could become an array of TEMPORARY allowed scripts

    printf("Recieved illegal call from %s", temp.stack[0].scriptcallobject.name);

  else

    echo("Money deposited ^^");

}

Twinny/test and Twinny/Test2

PHP Code:


		
			
function onCreated() 

  Bank.deposit();

Result!

PHP Code:


		
			
Weapon/GUI-script Twinny/Test2 added/updated by Twinny

Recieved illegal call from Twinny/Test2

Weapon/GUI-script Twinny/Test added/updated by Twinny

Money deposited ^^

Oh, totally cool dude. I think there've been a few people awaiting the ability to view the callstack and script accordingly to improve script efficiencies. Though, I'm still with Twinny on protected/password protected variables, etc. this is an excellent addition!

I like this :) Great news. I'll start implementing into my MUDlib right away.

uhm, may i request that triggers are traced too? :p

Here are two functions, one to get the object that calls the function that calls it, and one to get the calling function in the same way.

PHP Code:


		
			
function getcallingfunction() {
  temp.callstack = getcallstack();
  return temp.callstack[temp.callstack.size() - 3];
}
function getcallingobject() {
  temp.callstack = getcallstack();
  return temp.callstack[temp.callstack.size() - 3].scriptcallobject;
}

Quote:

Originally Posted by projectigi (Post 1369290)

uhm, may i request that triggers are traced too? :p

Triggers are meant to be insecure, for easy script interaction. Also npcs could trigger each other endlessly. It could eventually be possible to find out who has triggered it.

well i just want to make sure that e.g. a onActionServerSide can only be called from the same weapon xD

Very nice, I love it.
Now I just want to be able to use it on Maloria :)

I missed this completely, very nice function! :D

Quote:

Originally Posted by xXziroXx (Post 1414528)

I missed this completely, very nice function! :D

Me too, thanks for bringing it to light :O

Quote:

Originally Posted by xXziroXx (Post 1414528)

I missed this completely, very nice function! :D

Same, didn't even notice it o.O

Couldn't have provided that first class bump without Dusty. :cool: