Pdb breakpoints don't work on lines without bytecode

[inducer]

BPO	6322
Nosy	@birkenfeld, @asvetlov, @xdegaye

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

Show more details

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2009-06-22.14:09:13.334>
labels = ['type-bug', 'library']
title = "Pdb breakpoints don't work on lines without bytecode"
updated_at = <Date 2012-11-24.11:01:15.525>
user = 'https://bugs.python.org/inducer'

bugs.python.org fields:

activity = <Date 2012-11-24.11:01:15.525>
actor = 'xdegaye'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2009-06-22.14:09:13.334>
creator = 'inducer'
dependencies = []
files = []
hgrepos = []
issue_num = 6322
keywords = []
message_count = 5.0
messages = ['89597', '109903', '171826', '172878', '176278']
nosy_count = 4.0
nosy_names = ['georg.brandl', 'inducer', 'asvetlov', 'xdegaye']
pr_nums = []
priority = 'normal'
resolution = None
stage = 'needs patch'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue6322'
versions = ['Python 3.1', 'Python 2.7', 'Python 3.2']

Linked PRs

• gh-50571: Check bytecode before accepting a breakpoint in pdb #145121

[inducer]

Take this program:

8< -----------------------------------------------
print "START"

a = [
        1
        for i in range(10)]
8< 

---

as "a.py", run "python -m pdb a.py", say "b 3" to set a breakpoint on
line 3. Say "c" to start execution. Watch the program finish without
ever hitting the breakpoint.

The problem is that line 3 has no bytecode generated for it, so there's
nothing to break on. Pdb should provide feedback in this case. I'm the
author of PuDB, and I've written code to check for this condition Please
feel free to steal that code, here:

http://is.gd/19fvD

[BreamoreBoy]

The OP has offered source code which fixes this issue, see msg89597.

[xdegaye]

Another example where pdb does not stop at breakpoints set at
global, else and finally statements:

$ nl -ba foo.py
     1  x = 1
     2  def main():
     3      global x
     4      try:
     5          if not x:
     6              x = 2
     7          else:
     8              x = 3
     9      finally:
    10          x = 4
    11
    12  if __name__ == "__main__":
    13      main()
    14      print(x)
    15
$ python3 -m pdb foo.py
> /path_to/foo.py(1)<module>()
-> x = 1
(Pdb) break 3
Breakpoint 1 at /path_to/foo.py:3
(Pdb) break 7
Breakpoint 2 at /path_to/foo.py:7
(Pdb) break 9
Breakpoint 3 at /path_to/foo.py:9
(Pdb) break 14
Breakpoint 4 at /path_to/foo.py:14
(Pdb) continue
> /path_to/foo.py(14)<module>()
-> print(x)
(Pdb)

==============
vim:sts=2:sw=2

[xdegaye]

This is fixed in the proposed patch named pdb_lnotab.patch attached to
bpo-14913.

[xdegaye]

See also how this is fixed at
http://code.google.com/p/pdb-clone/source/detail?r=6b342324ebdc4558b83b9391e34478c1fa0752db

[devdanzin]

The first example doesn't repro in main, but the second one does.