Turtle module crashes python

[terryjreedy]

BPO	7074
Nosy	@loewis, @terryjreedy, @abalkin, @willingc
Superseder	bpo-11029: Crash, 2.7.1, Tkinter and threads and line drawing
Files	turtlecrash.py

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2017-05-29.07:08:10.535>
created_at = <Date 2009-10-06.23:39:18.526>
labels = ['type-bug', 'library']
title = 'Turtle module crashes python'
updated_at = <Date 2017-05-29.07:08:10.534>
user = 'https://github.com/terryjreedy'

bugs.python.org fields:

activity = <Date 2017-05-29.07:08:10.534>
actor = 'terry.reedy'
assignee = 'none'
closed = True
closed_date = <Date 2017-05-29.07:08:10.535>
closer = 'terry.reedy'
components = ['Library (Lib)']
creation = <Date 2009-10-06.23:39:18.526>
creator = 'terry.reedy'
dependencies = []
files = ['15060']
hgrepos = []
issue_num = 7074
keywords = []
message_count = 8.0
messages = ['93669', '93670', '127682', '127684', '127971', '183771', '294670', '294676']
nosy_count = 5.0
nosy_names = ['loewis', 'terry.reedy', 'belopolsky', 'gregorlingl', 'willingc']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = '11029'
type = 'behavior'
url = 'https://bugs.python.org/issue7074'
versions = ['Python 3.2', 'Python 3.3']

[terryjreedy]

Attached file run from IDLE edit window with 3.1, winxp works fine--
turtle moves in response to cursor keys-- if quit soon enough.
But after about 1000 key repeats, pythonw crashes with standard MSVC++
runtime error window, pythonw error window, and IDLE shell window
trackback ending with "RuntimeError: maximum recursion depth exceeded
while calling a Python object". The full traceback in appended to the file.

Disabling the undo buffer did not solve the problem.

Running the file from regular interpreter with

>>exec(open(filename,'r').read())

gave essentially same result -- same traceback with slightly different
associated messages, so it is not an IDLE problem.

The demo/test at the bottem of turtle.py works fine -- but it does not
run as long.

I do not see the recursion, but calling the configuration merge with
every movement seems fishy.

[terryjreedy]

resubmitting file

[abalkin]

I can reproduce the crash on OSX. After ~ 100 keystrokes, I get the following diagnostics:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/tkinter/__init__.py", line 1399, in __call__
    return self.func(*args)
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 701, in eventfun
    fun()
  File "turtlecrash.py", line 12, in klt
    def klt(): seth(180); fd(vel)
  File "<string>", line 1, in seth
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 1936, in setheading
    self._rotate(angle)
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 3277, in _rotate
    self._update()
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 2660, in _update
    self._update_data()
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 2651, in _update_data
    self._pencolor, self._pensize)
  File "/Users/sasha/Work/python-svn/py3k-commit/Lib/turtle.py", line 545, in _drawline
    self.cv.coords(lineitem, *cl)
  File "<string>", line 1, in coords
RuntimeError: maximum recursion depth exceeded
Fatal Python error: Cannot recover from stack overflow.
Abort trap

[abalkin]

This looks like a duplicate of bpo-11029. It is not safe to call graphic primitives in event callbacks. A workaround is described at <http://effbot.org/zone/tkinter-threads.htm\>.

[terryjreedy]

This is not a duplicate because this issue is about the stdlib turtle module doing something wrong and needing to be fixed. Also, this issue does not involve threads, at least none that I starting.

"It is not safe to call graphic primitives in event callbacks."

This is a confusing statement. The tutorial at
http://www.tkdocs.com/tutorial/canvas.html
by an experienced tk developer (19 years) includes this:

def addLine(event):
    global lastx, lasty
    canvas.create_line((lastx, lasty, event.x, event.y))
    lastx, lasty = event.x, event.y

Is canvas.create_line a primitive or not?

At the very least, unless I missed something, some change to turtle doc is needed.

[terryjreedy]

"It is not safe to call graphic primitives in event callbacks."
Martin, do you agree that this is (or should be) the case?

[willingc]

Ran the turtlecrash.py example with Python 3.6 on MacOS 10.12.4. I was unable to create a crash using keypresses. I recommend closing as 3.2 has reached EOL and 3.3 will reach EOL in less than 5 months. I'm going to change status to Pending and Resolution to out of date. I will close in 2 weeks if there is no further feedback on the issue. Thanks.

[terryjreedy]

I copied and pasted my code from turtlecrash.py into 3.7 editor, ran, and probably held key down for 3000 clicks, and it worked as it should.