Tracing Function Invocations

[Daniel Gredler]

Hi guys,

I'm trying to use the jsdIDebuggerService interface in a Firefox extension
to trace function invocations. Specifically, I'm using the debugger
service's functionHook. This hook takes two arguments: the current frame and
the invocation type.

However, I'm having trouble accessing the name of the function being
invoked, as well as the names and values of the arguments being passed to
the function. The problem is that frame.functionName and
frame.script.functionObject refer to the function within which the
invocation is made, not the function being invoked.

Has anyone used the functionHook to trace and/or log JavaScript function
calls? If not, has anyone used a different method to do achieve this? I'm
attaching a snippet of code below so as to give a better idea of what I'm
doing (wrong).

Take care,

Daniel



var functionHook = function(frame, type) {
    if(type != jsdICallHook.TYPE_FUNCTION_CALL) return;
    // Start with indentation.
    var s = "";
    var parent = frame.callingFrame;
    while(parent) {
        if(!parent.isDebugger && !parent.isNative) s += "   ";
        parent = parent.callingFrame;
    }
    // Continue with argument info.
    var args = "";
    var p = new Object();
    frame.script.functionObject.getProperties(p, {});
    p = p.value;
    for(var i = p.length - 1; i >= 0; i--) {
        if(p[i].flags & jsdIProperty.FLAG_ARGUMENT) {
            args += p[i].name.stringValue + ": " + formatValue(p[i].value) +
", ";
        }
    }
    if(args.lastIndexOf(", ") == args.length - 2) {
        args = args.substring(0, args.length - 2);
    }
    // Continue with other information.
    var line = frame.line;
    var funcName = frame.functionName;
    // Log the gathered information.
    s += funcName + "(" + args + ") @ line " + line + " of " + file;
    ftLog.push(s);
}
debuggerService.on();
debuggerService.functionHook = { onCall: functionHook };

--
Daniel Gredler
http://daniel.gredler.net/
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[John J Barton]

Daniel Gredler wrote:

> Hi guys,
>
> I'm trying to use the jsdIDebuggerService interface in a Firefox extension
> to trace function invocations. Specifically, I'm using the debugger
> service's functionHook. This hook takes two arguments: the current frame and
> the invocation type.
>
> However, I'm having trouble accessing the name of the function being
> invoked, as well as the names and values of the arguments being passed to
> the function. The problem is that frame.functionName and
> frame.script.functionObject refer to the function within which the
> invocation is made, not the function being invoked.
>
> Has anyone used the functionHook to trace and/or log JavaScript function
> calls? If not, has anyone used a different method to do achieve this? I'm
> attaching a snippet of code below so as to give a better idea of what I'm
> doing (wrong).
>

You can look at firebug-service.js in
http://code.google.com/p/fbug/source/browse/branches/firebug1.2/components/firebug-service.js
to see how step-in, step-out etc are implemented.

John.
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[Daniel Gredler]

Hi John,

Based on the Firebug code, it looks like I need to hook the function
invocations, and when a function is called, hook execution (interrupts). I
can then get all the info I need in the interrupt, and unhook interrupts
until the next function call. I had hoped that there was a better way, but
it seems to work. Thanks for your help!

Regards,

Daniel



On Mon, Feb 18, 2008 at 9:35 PM, John J. Barton <johnjbarton@...>
wrote:

> Daniel Gredler wrote:
> > Hi guys,
> >
> > I'm trying to use the jsdIDebuggerService interface in a Firefox
> extension
> > to trace function invocations. Specifically, I'm using the debugger
> > service's functionHook. This hook takes two arguments: the current frame
> and
> > the invocation type.
> >
> > However, I'm having trouble accessing the name of the function being
> > invoked, as well as the names and values of the arguments being passed
> to
> > the function. The problem is that frame.functionName and
> > frame.script.functionObject refer to the function within which the
> > invocation is made, not the function being invoked.
> >
> > Has anyone used the functionHook to trace and/or log JavaScript function
> > calls? If not, has anyone used a different method to do achieve this?
> I'm
> > attaching a snippet of code below so as to give a better idea of what
> I'm
> > doing (wrong).
> >
> You can look at firebug-service.js in
>
> http://code.google.com/p/fbug/source/browse/branches/firebug1.2/components/firebug-service.js
> to see how step-in, step-out etc are implemented.
>
> John.
> _______________________________________________
> dev-apps-js-debugger mailing list
> dev-apps-js-debugger@...
> https://lists.mozilla.org/listinfo/dev-apps-js-debugger
>

--
Daniel Gredler
http://daniel.gredler.net/
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