Question

This is a followup to Clojure: Compile time insertion of pre/post functions

My goal is to call a debug function instead of throwing an exception. I am looking for the best way to store a list of stack frames, function calls and their arguments, to accomplish this.

I want to have a function (my-uber-debug), so that when I call it (instead of throwing an exception), the following things happen:

• a new Java window pops up
• there is a record of the current clojure stack frame
• for each stack frame, there is a record of the argument passed to the function

This is so that I can move up/down the stack frames, and examine the arguments passed to get to this current point. [If somehow, magically, we can get the variables defined in “let” environments, that’d be awesome too.]

Current Idea

I’m going to have a thread local variable uber-debug, which has type:
List of StackFrames
where StackFrame = function + arguments

At each function call, it’s going to push (cons the current function + arguments to uber-debug), then at the end of a function call, it’s going to remove the first element from uber-debug

Then, when I call (my-uber-debug), it just pops up a new java window, and lets me interact with uber-debug

Question

The ideas I’ve had so far are probably not ideal for setting this up. What is the right way to solve this problem?

Edit:

The question is NOT about the Swing/GUI part. It’s about how to store the stack frames.

Thanks!

Answer 1

Your answer may depend on a lot of factors, so I am going to answer this by giving you my thoughts.

If you merely want to store function calls and their parameters when an exception occurs, then either write a macro or function as a wrapper to accomplish this. You would then have to pass all functions to be called to this wrapper. The wrapper would perform the try catch operation and whatever else you need.

You might also want to look into Clojure meta data in addition to writing the wrapper, because your running code could look at its meta-data and make some decisions based on that as well. I have never used meta data, but the information at the link looks promising.

As a final thought, it might be helpful for you to further delineate what you want to accomplish by doing this by editing your original post and putting the information there.

For example, are these stack traces for a library or a main program?

As to storing all this information, are multiple threads going to need it, or just one?

Can you get by storing the information in a let binding at the highest level of your program, or do you need something like a ref?