py-bt errors on backtrace with PyRun_SimpleString and friends

[pmuldoon]

BPO	18213
Nosy	@ngie-eign, @davidmalcolm, @iritkatriel

^{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 = 'https://github.com/davidmalcolm'
closed_at = <Date 2020-11-30.00:09:20.042>
created_at = <Date 2013-06-14.14:07:25.778>
labels = ['type-crash']
title = 'py-bt errors on backtrace with PyRun_SimpleString and friends'
updated_at = <Date 2020-11-30.00:09:20.042>
user = 'https://bugs.python.org/pmuldoon'

bugs.python.org fields:

activity = <Date 2020-11-30.00:09:20.042>
actor = 'iritkatriel'
assignee = 'dmalcolm'
closed = True
closed_date = <Date 2020-11-30.00:09:20.042>
closer = 'iritkatriel'
components = ['Demos and Tools']
creation = <Date 2013-06-14.14:07:25.778>
creator = 'pmuldoon'
dependencies = []
files = []
hgrepos = []
issue_num = 18213
keywords = []
message_count = 5.0
messages = ['191131', '191136', '191138', '361454', '382098']
nosy_count = 5.0
nosy_names = ['ngie', 'dmalcolm', 'tromey', 'pmuldoon', 'iritkatriel']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue18213'
versions = ['Python 2.7']

[pmuldoon]

(gdb) py-bt

#2 Frame 0xef8180, for file <string>, line 1, in <module> ()
Python Exception <type 'exceptions.IOError'> (2, 'No such file or directory', '<string>'):
Error occurred in Python command: (2, 'No such file or directory', '<string>')

This is the actual raw frame data:

#0 frapy_pc (self=<gdb.Frame at remote 0x7ffff1ab28b0>, args=0x0) at ../../gdb/gdb/python/py-frame.c:223
#1 0x0000003edf4dcfd6 in call_function (oparg=<optimized out>, pp_stack=0x7fffffffd378) at /usr/src/debug/Python-2.7.3/Python/ceval.c:4082
#2 PyEval_EvalFrameEx (f=f@entry=Frame 0xef8180, for file <string>, line 1, in <module> (), throwflag=throwflag@entry=0)
at /usr/src/debug/Python-2.7.3/Python/ceval.c:2740
#3 0x0000003edf4ddcbf in PyEval_EvalCodeEx (
During symbol reading, Multiple children of DIE 0x3904c refer to DIE 0x38d87 as their abstract origin.
co=co@entry=0x7ffff1adb8b0, globals=globals@entry=
{'g': <gdb.Frame at remote 0x7ffff1ab28b0>, '__builtins__': <module at remote 0x7ffff1ba9ad0>, 'GdbRemoveReadlineFinder': <classobj at remote 0x7ffff1ac81f0>, '__package__': None, 'sys': <module at remote 0x7ffff1ba9b78>, 'gdb': <module at remote 0x7ffff1af2130>, '__name__': '__main__', '__doc__': None}, locals=locals@entry=
{'g': <gdb.Frame at remote 0x7ffff1ab28b0>, '__builtins__': <module at remote 0x7ffff1ba9ad0>, 'GdbRemoveReadlineFinder': <classobj at remote 0x7ffff1ac81f0>, '__package__': None, 'sys': <module at remote 0x7ffff1ba9b78>, 'gdb': <module at remote 0x7ffff1af2130>, '__name__': '__main__', '__doc__': None}, args=args@entry=0x0, argcount=argcount@entry=0, kws=kws@entry=0x0, kwcount=kwcount@entry=0, defs=defs@entry=0x0,
defcount=defcount@entry=0, closure=closure@entry=0x0) at /usr/src/debug/Python-2.7.3/Python/ceval.c:3330

[davidmalcolm]

pmuldoon: did you truncate the output of bt? (or did the superior gdb you're using do this behind the scenes? I know you hack on gdb itself, and this looks a superior gdb debugging an inferior gdb).

The reason for this error:

Python Exception <type 'exceptions.IOError'> (2, 'No such file or directory', '<string>'): 

is that py-bt is attempting to print the line of source code that the frame is at, but the source was provided as a string, not a file, presumably due to a call to PyRun_SimpleString et al.

Python sets the filename of such code to be the dummy name "<string>", and py-bt attempts to use that as a real filename and open it, failing (unless you happen to have a file named "<string>" in which case it tries to list it).

[pmuldoon]

Yes I did truncate the output, the backtrace was very long.

This is my scenario:

gdb --args ./gdb <somefile>

When the superior gdb loads, I did:

(top-gdb) b frapy_pc
(top-gdb) run

In the inferior gdb, I did:

(gdb) start
(gdb) py g = gdb.selected_frame()
(gdb) py print g.pc()

This will hit the breakpoint in the inferior gdb and you will be returned to the superior gdb. I then did:

(top-gdb) py-bt

[ngie-eign]

This particular issue has been resolved in python 3.x.

[iritkatriel]

Python 2-only issue.