On 13 January 2014 09:08, Fabio Zadrozny <fabiofz@gmail.com> wrote:
Hi Python-dev.
I'm playing a bit on the concept on live-coding during a debug session and one of the most annoying things is that although I can reload the code for a function (using something close to xreload), it seems it's not possible to change the code for the current frame (i.e.: I need to get out of the function call and then back in to a call to the method from that frame to see the changes).
I gave a look on the frameobject and it seems it would be possible to set frame.f_code to another code object -- and set the line number to the start of the new object, which would cover the most common situation, which would be restarting the current frame -- provided the arguments remain the same (which is close to what the java debugger in Eclipse does when it drops the current frame -- on Python, provided I'm not in a try..except block I can do even better setting the the frame.f_lineno, but without being able to change the frame f_code it loses a lot of its usefulness).
So, I'd like to ask for feedback from people with more knowledge on whether it'd be actually feasible to change the frame.f_code and possible implications on doing that.
Huh, I would have sworn there was already an issue on the tracker about that, but it appears not (Eric Snow has one about adding a reference to the running function, but nothing about trying to switch an executing frame: http://bugs.python.org/issue12857). Anyway, your main problem isn't the reference to the code object from the frame: it's the fact that the main eval loop has a reference to that code object from a C level stack variable, and stores a bunch of other state directly on the C stack. I don't see anything *intrinsically* impossible about the idea, it just wouldn't be easy, since you'd have to come up with a way of dealing with that C level state that didn't slow down normal operation. Cheers, Nick. -- Nick Coghlan | ncoghlan@gmail.com | Brisbane, Australia