trace function not set, causing some Pdb commands to fail

[xdegaye]

BPO	14728
Nosy	@loewis, @birkenfeld, @terryjreedy, @orsenthil, @asvetlov, @xdegaye
Files	pdb.patch pdb_default.patch pdb_2.7.patch

^{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 = None
created_at = <Date 2012-05-05.10:43:44.908>
labels = ['type-bug', 'library']
title = 'trace function not set, causing some Pdb commands to fail'
updated_at = <Date 2012-12-05.11:07:49.874>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2012-12-05.11:07:49.874>
actor = 'asvetlov'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2012-05-05.10:43:44.908>
creator = 'xdegaye'
dependencies = []
files = ['25459', '25463', '25464']
hgrepos = []
issue_num = 14728
keywords = ['patch']
message_count = 5.0
messages = ['159985', '159997', '159998', '160417', '176277']
nosy_count = 7.0
nosy_names = ['loewis', 'georg.brandl', 'terry.reedy', 'orsenthil', 'asvetlov', 'neologix', 'xdegaye']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue14728'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']

Linked PRs

• gh-58933: Make pdb return to caller frame correctly when f_trace is not set #118979
• [3.13] gh-58933: Make pdb return to caller frame correctly when f_trace is not set (GH-118979) #119007
• [3.12] gh-58933: Make pdb return to caller frame correctly when f_trace is not set (GH-118979) #119008

[xdegaye]

The bpo-13183 raises the problem that when the trace function is not
set in the caller frame, the step command fails at a return statement.

This new issue raises the point that, for the same reason:

* the next, until and return statements fail also at a return
  statement when the caller frame does not have a trace function

* when the user runs the up and down commands at any line in a
  frame to select a new frame, then the next, until or return
  commands fail when the selected frame does not have a trace
  function

The attached patch fixes all those problems (by first removing the
changes made in bdb.py at bpo-13183).

After the patch, the implementation ensures now that self.stopframe is
either None, or belongs to the stack frame in the interval
[self.botframe, self._curframe] and that it is set to self.botframe
when the debugging session terminates. This allows removing the while
loop in stop_here with an improvement in the performance of Pdb (since
stop_here may be called at each line, even when no breakpoint is set
in the function).

The patch applies to the default branch and includes 5 new test cases.
A patch for 2.7 will be submitted later.

[xdegaye]

Uploaded pdb_default.patch that applies on the default branch with
minor changes to the initial pdb.patch.

[xdegaye]

Uploaded pdb_2.7.patch that applies on the 2.7 branch.

[terryjreedy]

Since this pdb issue is a continuation of bpo-13183 and repeals a part of that issue's patch, I nosy'ed the contributors to that issue.

[xdegaye]

See also how this is fixed at
http://code.google.com/p/pdb-clone/source/detail?r=4a6d8f2515eed16347d2e2c304e1942585427d50