[Python-Dev] about line numbers

[Christian Tismer]

Guido van Rossum wrote:
> 
> Earlier, you argued that this is "not an optimization," but rather
> avoiding redundancy.  I should have responded right then that I
> disagree, or at least I'm lukewarm about your patch.  Either you're
> not using -O, and then you don't care much about this; or you care,
> and then you should be using -O.
> 
> Rather than encrusting the code with more and more ad-hoc micro
> optimizations, I'd prefer to have someone look into Tim's suggestion
> of supporting more efficient breakpoints...

I didn't think of this before, but I just realized that
I have something like that already in Stackless Python.
It is possible to set a breakpoint at every opcode, for every
frame. Adding an extra opcode for breakpoints is a good thing
as well. The former are good for tracing, conditionla breakpoints
and such, and cost a little more time since the is always one extra
function call. The latter would be a quick, less versatile thing.

The implementation of inserting extra breakpoint opcodes for
running code turns out to be easy to implement, if the running
frame gets a local extra copy of its code object, with the
breakpoints replacing the original opcodes. The breakpoint handler
would then simply look into the original code object.

Inserting breakpoints on the source level gives us breakpoints
per procedure. Doing it in a running frame gives "instance" level
debugging of code. Checking a monitor function on every opcode
is slightly more expensive but most general.
We can have it all, what do you think.
I'm going to finish and publish the stackless/continous package
and submit a paper by end of September. Should I include
this debugging feature?

ciao - chris

-- 
Christian Tismer             :^)   <mailto:tismer@appliedbiometrics.com>
Applied Biometrics GmbH      :     Have a break! Take a ride on Python's
Kaiserin-Augusta-Allee 101   :    *Starship* http://starship.python.net
10553 Berlin                 :     PGP key -> http://wwwkeys.pgp.net
PGP Fingerprint       E182 71C7 1A9D 66E9 9D15  D3CC D4D7 93E2 1FAE F6DF
     we're tired of banana software - shipped green, ripens at home