[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Georg Brandl]

Georg Brandl  added the comment:

Committed rest of patch in r87045.  Will try to get test_pdb2 in shape and 
working on all platforms.

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resolution:  -> accepted
status: open -> closed

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

The patch tries to write to stdout in signal handler. 

This currently does not work in the python 3.x  (see
http://bugs.python.org/issue10478).

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Georg Brandl]

Georg Brandl  added the comment:

Adding the rest of the patch adapted for py3k trunk as of today.

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keywords: +patch
Added file: http://bugs.python.org/file18277/pdb-keyboardinterrupt.diff

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Georg Brandl]

Georg Brandl  added the comment:

I committed the "commands" part of the patch in r83308.

For the SIGINT part, I'm concerned that the SIGINT handler is set
in the Pdb constructor, since it's a processwide setting I think it
should a) be set only before sys.settrace() and b) be restored appropriately 
when debugging is finished.

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nosy: +georg.brandl

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

I tried to understand the cause of failures and I don't see how test_pdb2 could 
have caused them ;-).

Here is the relevant part of buildbot timeline:

http://www.python.org/dev/buildbot/trunk/?last_time=1273368351&show_time=7400

The only test failures which have  log files were sparc solaris 10 and ia64 and 
both failures were in test_unittest. All other buildbot failures don't have 
test logs associated with them..

Is there a way to  access test logs for other platforms?

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Gregory P. Smith]

Gregory P. Smith  added the comment:

And reverted in trunk r81013.  Multiple buildbot problems from the initial 
commit due to the unittest.

This is likely to be py3k only at this point.

I do believe sig.patch.v3 is fine, but its the test_pdb2 unittest that is 
difficult to make work well.

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versions:  -Python 2.7

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Gregory P. Smith]

Gregory P. Smith  added the comment:

Committed to trunk in r81012.  though as this missed 2.7beta2 its possible that 
will be rejected and this becomes a 3.x only feature.

I'm porting to py3k now.

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versions: +Python 3.2

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

a note on testing: it should be possible to integrate the tests into existing 
test_pdb.py by simply placing subprocess based tests next to doctest-based 
tests. This way pdb tests will at least be in a single module. (this is an 
approach taken by a patch in 
http://bugs.python.org/issue7964)

Would it be better?

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

Is there anything else I can do for this patch?

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

I'm attaching a test for Ctrl-C behavior on Linux (the patch itself works on 
Windows too, but I am not sure how to send Ctrl-C on windows programatically 
and subprocess does not have this functionality either).

The test_pdb2.py module is generic and can be extended to test other 
functionality. But, as discussed earlier, it cannot be easily (if at all) 
integrated into existing test_pdb.py.

Note that the test module will NOT work with existing pdb (as it doesnot have 
expected Ctrl-C) behavior, but on can specify alternative pdb location from 
command line:

  env DEBUG_PDB=./pdb.py ./test_pdb2.py

--
Added file: http://bugs.python.org/file16619/test_pdb2.py

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

> Also, can you take a look at how the pdb unittests work and see if you
can come up with a way to unittest the KeyboardInterrupt behavior?

Yes, this is doable. In fact, I already have such tests written (unix only 
though). The tests are assert based but it should not be difficult to convert 
them to unittest. Moreover, I have many more tests for pdb written in the same 
style. 

However, these tests are not easily (and possibly not at all) integratable with 
existing test_pdb.py module. (See below for the problems). So would it be 
acceptable to have these tests as a separate module (test_pdb2.py or some 
such)? (I might also need some help with integrating the module)

Background
--

Here is the basic problem: testing/debugging a debugger is hard by itself (you 
need to deal with 2 programs at once: the one being debugged and the debugger 
which run intermittently), now throw in doctest and it becomes much harder (as 
everything you do now gets covered by another layer). And now we need to test 
signals and some of the tests will likely be platform specific which makes it 
even worse. 

In contrast, in my tests the snippets of code are written into a tmp file and 
then are fed into debugger, the debugger itself is run as a subprocess. So if a 
test fails, it can be easily rerun under debugger manually and you can  test 
for things like pdb exits and stalls.

Here is a snippet from my pdb tests (just to give an idea how they would look 
like: essentially, send a command to pdb, check the response).


  pdb=PdbTester("pdb_t_hello","""\
  import time
  for i in xrange(1):
 time.sleep(0.05)
  """)

  pdb.pdbHandle.stdin.write("c\n")
  time.sleep(0.01)
  #pdb_t_hello running, try to interrupt it
  pdb.pdbHandle.send_signal(signal.SIGINT)
  pdb.waitForPrompt()
  pdb.queryAndMatch("p i", "0")
  pdb.query("n")
  pdb.query("n")
  pdb.queryAndMatch("p i", "1")
  pdb.query("s")
  pdb.query("s")
  pdb.queryAndMatch("p i","2")
  pdb.pdbHandle.stdin.write("c\n")
  time.sleep(0.03)
  pdb.pdbHandle.send_signal(signal.SIGINT)
  pdb.waitForPrompt()
  pdb.queryAndMatch("p i","3")

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

new version of the patch is uploaded to bugs.python.org

http://codereview.appspot.com/216067/diff/2001/2002
File Lib/pdb.py (right):

http://codereview.appspot.com/216067/diff/2001/2002#newcode63
Lib/pdb.py:63: def sigint_handler(self, signum, frame):
On 2010/02/28 20:12:00, gregory.p.smith wrote:
> Please move this below the __init__ definition.  It makes classes odd
to read
> when __init__ isn't the first method defined when people are looking
for the
> constructor to see how to use it.

Done.

http://codereview.appspot.com/216067/diff/2001/2002#newcode64
Lib/pdb.py:64: if self.allow_kbdint:
On 2010/02/28 20:12:00, gregory.p.smith wrote:
> Initialize self.allow_kdbint in __init__ so that a SIGINT coming in
before
> _cmdloop has run doesn't cause an AttributeError.

Done.

http://codereview.appspot.com/216067/diff/2001/2002#newcode215
Lib/pdb.py:215: # keyboard interrupts allow for an easy way to interrupt
On 2010/02/28 20:12:00, gregory.p.smith wrote:
> "to cancel the current command"

I changed the wording a bit, should be ok now.

http://codereview.appspot.com/216067/diff/2001/2002#newcode356
Lib/pdb.py:356: #it appears that that when pdb is reading input from a
pipe
On 2010/02/28 20:12:00, gregory.p.smith wrote:
> Space after the # please.

this code
> is?

particular
> interrupted command from the list of commands to run at the current
breakpoint
> but I may be misreading things as I haven't spent much time in pdb.py.

Done. I've also added a comment to explain what's going on.

http://codereview.appspot.com/216067/show

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Ilya Sandler]

Ilya Sandler  added the comment:

Another version of the patch is attached ( I think, I fixed all the remaining 
style issues).

I'll answer the testing question in a separate post

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Added file: http://bugs.python.org/file16470/sig.patch.v3

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[issue7245] better Ctrl-C support in pdb (program can be resumed) (issue216067)

[Gregory P. Smith]

Gregory P. Smith  added the comment:

Reviewers: gregory.p.smith, Benjamin, ilya.sandler,

Message:
Also, can you take a look at how the pdb unittests work and see if you
can come up with a way to unittest the KeyboardInterrupt behavior?

Particular for the 4 scenarios you outlined in your prior comments in
the bug (those all make sense to me).

http://codereview.appspot.com/216067/diff/2001/2002
File Lib/pdb.py (right):

http://codereview.appspot.com/216067/diff/2001/2002#newcode63
Lib/pdb.py:63: def sigint_handler(self, signum, frame):
Please move this below the __init__ definition.  It makes classes odd to
read when __init__ isn't the first method defined when people are
looking for the constructor to see how to use it.

http://codereview.appspot.com/216067/diff/2001/2002#newcode64
Lib/pdb.py:64: if self.allow_kbdint:
Initialize self.allow_kdbint in __init__ so that a SIGINT coming in
before _cmdloop has run doesn't cause an AttributeError.

http://codereview.appspot.com/216067/diff/2001/2002#newcode215
Lib/pdb.py:215: # keyboard interrupts allow for an easy way to interrupt
"to cancel the current command"

http://codereview.appspot.com/216067/diff/2001/2002#newcode356
Lib/pdb.py:356: #it appears that that when pdb is reading input from a
pipe
Space after the # please.

Also, could you add a comment in here describing what the effect of this
code is?

It looks like you catch KeyboardInterrupt here and remove the particular
interrupted command from the list of commands to run at the current
breakpoint but I may be misreading things as I haven't spent much time
in pdb.py.

Please review this at http://codereview.appspot.com/216067/show

Affected files:
   M Lib/pdb.py

Index: Lib/pdb.py
===
--- Lib/pdb.py  (revision 78520)
+++ Lib/pdb.py  (working copy)
@@ -13,8 +13,10 @@
  import re
  import pprint
  import traceback
+import signal

+
  class Restart(Exception):
  """Causes a debugger to be restarted for the debugged python  
program."""
  pass
@@ -58,6 +60,13 @@

  class Pdb(bdb.Bdb, cmd.Cmd):

+def sigint_handler(self, signum, frame):
+if self.allow_kbdint:
+raise KeyboardInterrupt()
+print >>self.stdout, "\nProgram interrupted. (Use 'cont' to  
resume)."
+self.set_step()
+self.set_trace(frame)
+
  def __init__(self, completekey='tab', stdin=None, stdout=None,  
skip=None):
  bdb.Bdb.__init__(self, skip=skip)
  cmd.Cmd.__init__(self, completekey, stdin, stdout)
@@ -72,6 +81,7 @@
  import readline
  except ImportError:
  pass
+signal.signal(signal.SIGINT, self.sigint_handler)

  # Read $HOME/.pdbrc and ./.pdbrc
  self.rcLines = []
@@ -176,7 +186,7 @@
  if not self.commands_silent[currentbp]:
  self.print_stack_entry(self.stack[self.curindex])
  if self.commands_doprompt[currentbp]:
-self.cmdloop()
+self._cmdloop()
  self.forget()
  return
  return 1
@@ -199,11 +209,22 @@
  self.interaction(frame, exc_traceback)

  # General interaction function
+def _cmdloop(self):
+while 1:
+try:
+# keyboard interrupts allow for an easy way to interrupt
+# cancel current command
+self.allow_kbdint = True
+self.cmdloop()
+self.allow_kbdint = False
+break
+except KeyboardInterrupt:
+print >>self.stdout, '--KeyboardInterrupt--'

  def interaction(self, frame, traceback):
  self.setup(frame, traceback)
  self.print_stack_entry(self.stack[self.curindex])
-self.cmdloop()
+self._cmdloop()
  self.forget()

  def displayhook(self, obj):
@@ -329,9 +350,18 @@
  prompt_back = self.prompt
  self.prompt = '(com) '
  self.commands_defining = True
-self.cmdloop()
-self.commands_defining = False
-self.prompt = prompt_back
+try:
+self.cmdloop()
+except (KeyboardInterrupt, IOError):
+#it appears that that when pdb is reading input from a pipe
+# we may get IOErrors, rather than KeyboardInterrupt
+self.commands.pop(bnum)   # remove this cmd list
+self.commands_doprompt.pop(bnum)
+self.commands_silent.pop(bnum)
+raise KeyboardInterrupt()
+finally:
+self.commands_defining = False
+self.prompt = prompt_back

  def do_break(self, arg, temporary = 0):
  # break [ ([filename:]lineno | function) [, "condition"] ]

--
title: better Ctrl-C support in pdb (program can be resumed) -> better Ctrl-C 
support in pdb (program can be resumed) (issue216067)

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