Pdb does not stop at a breakpoint set on the line of a function definition

[xdegaye]

BPO	14808
Nosy	@birkenfeld, @xdegaye
Files	pdb_default.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 2012-05-14.15:36:58.639>
labels = ['type-bug', 'library']
title = 'Pdb does not stop at a breakpoint set on the line of a function definition'
updated_at = <Date 2012-05-25.11:56:43.789>
user = 'https://github.com/xdegaye'

bugs.python.org fields:

activity = <Date 2012-05-25.11:56:43.789>
actor = 'xdegaye'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2012-05-14.15:36:58.639>
creator = 'xdegaye'
dependencies = []
files = ['25578']
hgrepos = []
issue_num = 14808
keywords = ['patch']
message_count = 2.0
messages = ['160629', '161574']
nosy_count = 2.0
nosy_names = ['georg.brandl', 'xdegaye']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue14808'
versions = ['Python 2.7', 'Python 3.2', 'Python 3.3']

Linked PRs

• gh-59013: Make line number of function breakpoint more precise #110582
• gh-59013: Set breakpoint on the first executable line in pdb when using break func #112470

[xdegaye]

In the following test both breakpoints are set on the line of a
function definition. However pdb does not stop when entering foo whose
breakpoint has been set with 'break 1' while pdb stops when entering
bar whose breakpoint has been set with 'break bar'. The breakpoint
table display is identical for both breakpoints. This is inconsistent
and confusing.

=== main.py ==================================
1 def foo():
2 pass
3
4 def bar():
5 pass
6
7 def main():
8 foo()
9 bar()
10
11 import pdb; pdb.runcall(main)
=================================================

$ python main.py
> /path_to/main.py(8)main()
-> foo()
(Pdb) break 1
Breakpoint 1 at /path_to/main.py:1
(Pdb) break bar
Breakpoint 2 at /path_to/main.py:4
(Pdb) break
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /path_to/main.py:1
2   breakpoint   keep yes   at /path_to/main.py:4
(Pdb) continue
> /path_to/main.py(5)bar()
-> pass
(Pdb) continue
$

=================================================

The reverse occurs in the following test where pdb stops only at the
execution of the function definition when the breakpoint has been set
with a line number.

=== main.py ==================================
1 x = 1
2
3 def foo():
4 pass
5
6 def bar():
7 pass
8
9 x = 2
=================================================

$ python -m pdb main.py
> /path_to/main.py(1)<module>()
-> x = 1
(Pdb) break 3
Breakpoint 1 at /path_to/main.py:3
(Pdb) break bar
Breakpoint 2 at /path_to/main.py:6
(Pdb) break 9
Breakpoint 3 at /path_to/main.py:9
(Pdb) break
Num Type         Disp Enb   Where
1   breakpoint   keep yes   at /path_to/main.py:3
2   breakpoint   keep yes   at /path_to/main.py:6
3   breakpoint   keep yes   at /path_to/main.py:9
(Pdb) continue
> /path_to/main.py(3)<module>()
-> def foo():
(Pdb) continue
> /path_to/main.py(9)<module>()
-> x = 2
(Pdb)

=================================================

The following patch fixes both inconsistencies by having pdb stop when
entering a function and at the execution of a definition whatever the
method used to set the breakpoint (line number or function name).

Two test cases are included in the patch.

[xdegaye]

Parsing the modules source seems a better way to fix this problem, see bpo-14913.

[gaogaotiantian]

With #110852, break func will assign the correct line number for function that is already defined.

[hugovk]

Fixed by #110582, thanks!

[gaogaotiantian]

Actually, there's still a case that's inconsistent. I did not figure out a solution then but I have a patch now. Let's reopen this and close it after the new PR is merged.

[gaogaotiantian]

With #112470 merged, this problem is fully fixed.