Re: What is wrong with Ada?

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Jean-Pierre Rosen <rosen@adalog.fr> writes:

> OK, take a typical example (of what I am doing, YMMV). In an ASIS
> program (AdaControl of course), I have a failure due to an
> "inappropriate element" to a given call, that I can easily identify from
> the stack trace. That place is called very often, just once in a while
> is the parameter incorrect. With a trace, I just have to read the last
> message befor the failure. But since I don't know beforehand how many
> times the sequence is called before failing, I would have to break on
> any occurrence - maybe hundreds. Not counting the fact that it is after
> I type "continue" that the program fails, and that I know that I just
> restarted from the point where I should have been investigating!

I used a debugger for OCaml that can execute backwards.  So you stop at
the failing assertion/check, and back up to see how you got there.
You can execute backward to a breakpoint, or single step backward.
Very useful in this sort of case.

In more primitive debuggers, you could still do various things without
using trace statements in the code.  E.g. you could set a breakpoint
on the assertion, and another on the failure of the assertion.
Disable the former.  Run.  Tell the debugger to print out the
count for the former.  Start over, with former enabled,
telling it to stop after N-1 times.  Now single-step
toward the bug.  Of course, if it's flaky, you're out of luck.

Having said all that -- I do sometimes use trace statements in the code.
E.g. when I suspect the debugger is telling a fib.  Or when I want
to analyze the log using editor searching or the like, after the fact.

- Bob