Steel Bank Common Lisp

> I want to see where my code is going wrong and I've tried doing
> trace, but it doesn't seem to want to work.
>
> Is there something else that I need to do to get trace working?

First of all, show us a sample session where you try to run trace
and get undesired results in response. :)

  Leslie

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2009/2/9 David Creelman <creelman.david@...>:

> I want to see where my code is going wrong and I've tried doing trace, but it
> doesn't seem to want to work.
>
> Is there something else that I need to do to get trace working?

Here's a trivial example:

* (defun fib (n) (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))

FIB
* (trace fib)

(FIB)
* (fib 4)
  0: (FIB 4)
    1: (FIB 3)
      2: (FIB 2)
        3: (FIB 1)
        3: FIB returned 1
        3: (FIB 0)
        3: FIB returned 0
      2: FIB returned 1
      2: (FIB 1)
      2: FIB returned 1
    1: FIB returned 2
    1: (FIB 2)
      2: (FIB 1)
      2: FIB returned 1
      2: (FIB 0)
      2: FIB returned 0
    1: FIB returned 1
  0: FIB returned 3
3

If you're still having trouble, please send more details.

Cheers,

 -- Nikodemus

2009/2/9 David Creelman <creelman.david@...>:

(I took the liberty of adding sbcl-help back to CC.)

> I have a function, check-reminders, that has an error in. I've added
> (trace check-reminders) just after the definition of the function. The trace
> seems to get registered, but when I run the function I don't get any traces.

Doing

  (defun foo () ...)
  (trace foo)

in a file, and not getting a trace when you call FOO sounds odd. A
session transcript would be helpful here. File or non-file scope is
not really an issue here: TRACE replaces the function definition with
a traced one.

> If I do the trace in another file that loads reminder-calcs, I get
>  0: (CHECK-REMINDERS 3328), but the function doesn't seem to get traced.
>
> reminder-calcs gets compiled and loaded via asdf.

This is from the traced function wrapper, so things *are* getting traced.

  0: (CHECK-REMINDERS 3328)

if there is no corresponding

  0: CHECK-REMINDERS returned ...

line, then perhaps CHECK-REMINDERS doesn't return normally, but unwinds?

> If I do (untrace) and then (trace) in a test file, I don't seem to get any
> traces either. I was kind of expecting everything to be traced with this
> approach. This makes me think that there is some other statement that I'm
> missing which will turn off optimization or include debugging data, but I'm
> not sure.

Plain (TRACE) does exactly nothing. To trace all functions in a
package you can do

  (trace "PACKAGE-NAME")

. Plain (UNTRACE) untraces everything.

Also: common reason for thing not being traced is inlining: inlined
calls to functions cannot be traced. If you have declaimed things
INLINE, TRACE will not work. Similarly, macros aren't ever traced (in
case that wasn't obvious.)

One additional possibility is *TRACE-OUTPUT* being bound or set to a
stream that doesn't show up in your REPL.

Cheers,

 -- Nikodemus

On Tue, Feb 10, 2009 at 02:08:59PM +0200, Nikodemus Siivola wrote:
> 2009/2/9 David Creelman <creelman.david@...>:
> 
> (I took the liberty of adding sbcl-help back to CC.)
Thanks for that.
> 
> > I have a function, check-reminders, that has an error in. I've added
> > (trace check-reminders) just after the definition of the function. The trace
> > seems to get registered, but when I run the function I don't get any traces.
> 
> Doing
> 
>   (defun foo () ...)
>   (trace foo)
> 
> in a file, and not getting a trace when you call FOO sounds odd. A
> session transcript would be helpful here. File or non-file scope is
> not really an issue here: TRACE replaces the function definition with
> a traced one.
> 
> > If I do the trace in another file that loads reminder-calcs, I get
> >  0: (CHECK-REMINDERS 3328), but the function doesn't seem to get traced.
> >
> > reminder-calcs gets compiled and loaded via asdf.
> 
> This is from the traced function wrapper, so things *are* getting traced.
Yes, I just misread it.
> 
>   0: (CHECK-REMINDERS 3328)
> 
> if there is no corresponding
> 
>   0: CHECK-REMINDERS returned ...
> 
> line, then perhaps CHECK-REMINDERS doesn't return normally, but unwinds?
It looks like this is what was happening. After I fixed the bug, I got the
following in my log

0: (CHECK-REMINDERS 3329)
  0: CHECK-REMINDERS returned

The bug was in check-reminders, but I misread the first of the above two lines 
and thought they were something that happened when I requested the trace. 
But it was doing exactly the right thing and logging that it had entered 
check-reminders, then breaking on the error.

The error turned out to be passing nil as the second arg to /. It reported it
as Y not set to a value. I had a Y var in my code, so I thought I had not set
it. It looks like it was more likely Y of something like 
(defun / (x y) (code ...)).

> 
> > If I do (untrace) and then (trace) in a test file, I don't seem to get any
> > traces either. I was kind of expecting everything to be traced with this
> > approach. This makes me think that there is some other statement that I'm
> > missing which will turn off optimization or include debugging data, but I'm
> > not sure.
> 
> Plain (TRACE) does exactly nothing. To trace all functions in a
> package you can do
> 
>   (trace "PACKAGE-NAME")
Okay, that might be useful next time. Thanks.
> 
> . Plain (UNTRACE) untraces everything.
> 
> Also: common reason for thing not being traced is inlining: inlined
> calls to functions cannot be traced. If you have declaimed things
> INLINE, TRACE will not work. Similarly, macros aren't ever traced (in
> case that wasn't obvious.)
Okay, that makes sense. In this case, that wasn't the problem.
> 
> One additional possibility is *TRACE-OUTPUT* being bound or set to a
> stream that doesn't show up in your REPL.
This wasn't happening either, but I'll remember that too.

Thanks for your help and the extra info on trace.

Regards
David

> 
> Cheers,
> 
>  -- Nikodemus