Python PDB `set_trace()` Doesn't Work Due to `lldb_editline`

[lambdaknight]

When trying to call pdb.set_trace() in a script in LLDB, I get an error about the lldb_editline module not having the attribute set_completer_delims.

polaris ➜  ~  lldb --version
lldb version 12.0.1
polaris ➜  ~  lldb
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> import sys;
>>> sys.executable
'/usr/bin/python3'
>>> sys.version
'3.6.8 (default, Jan 25 2023, 15:03:30) \n[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)]'
>>> import pdb
>>> pdb.set_trace()
Traceback (most recent call last):
  File "/usr/lib64/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/usr/lib64/python3.6/pdb.py", line 1585, in set_trace
    Pdb().set_trace(sys._getframe().f_back)
  File "/usr/lib64/python3.6/pdb.py", line 156, in __init__
    readline.set_completer_delims(' \t\n`@#$%^&*()=+[{]}\\|;:\'",<>?')
AttributeError: module 'lldb_editline' has no attribute 'set_completer_delims'

If I run the same version of python from the command line, I get the following:

polaris ➜  ~  python3.6
Python 3.6.8 (default, Jan 25 2023, 15:03:30) 
[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.executable
'/usr/bin/python3.6'
>>> sys.version
'3.6.8 (default, Jan 25 2023, 15:03:30) \n[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)]'
>>> import pdb
>>> pdb.set_trace()
--Return--
> <stdin>(1)<module>()->None
(Pdb) 

If I try to manually load the local readline module, LLDB just seg faults.

polaris ➜  ~  lldb
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> import importlib.util
>>> import sys
>>> spec = importlib.util.spec_from_file_location("readline", "/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so")
>>> spec
ModuleSpec(name='readline', loader=<_frozen_importlib_external.ExtensionFileLoader object at 0x7f22a63889b0>, origin='/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so')
>>> foo = importlib.util.module_from_spec(spec)
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0.      Program arguments: lldb
 #0 0x00007f22b9fffa00 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/lib64/libLLVM-12.so+0xb4fa00)
 #1 0x00007f22b9ffd5c4 llvm::sys::RunSignalHandlers() (/lib64/libLLVM-12.so+0xb4d5c4)
 #2 0x00007f22b9ffe155 (/lib64/libLLVM-12.so+0xb4e155)
 #3 0x00007f22c34a4cf0 __restore_rt (/lib64/libpthread.so.0+0x12cf0)
 #4 0x00007f22b838aad4 PyModule_GetState (/lib64/libpython3.6m.so.1.0+0x110ad4)
 #5 0x00007f22a556a63d (/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so+0x463d)
 #6 0x00007f22b7264ca5 rl_initialize (/lib64/libedit.so.0+0x1eca5)
 #7 0x00007f22a556aa1d PyInit_readline (/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so+0x4a1d)
 #8 0x00007f22b8478bd2 _PyImport_LoadDynamicModuleWithSpec (/lib64/libpython3.6m.so.1.0+0x1febd2)
 #9 0x00007f22b8478dd1 (/lib64/libpython3.6m.so.1.0+0x1fedd1)
#10 0x00007f22b840ed92 PyCFunction_Call (/lib64/libpython3.6m.so.1.0+0x194d92)
#11 0x00007f22b841c98d _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x1a298d)
#12 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#13 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#14 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#15 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#16 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#17 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#18 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#19 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#20 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#21 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#22 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#23 0x00007f22b8374d33 PyEval_EvalCode (/lib64/libpython3.6m.so.1.0+0xfad33)
#24 0x00007f22b8484ec0 (/lib64/libpython3.6m.so.1.0+0x20aec0)
#25 0x00007f22b8415de7 (/lib64/libpython3.6m.so.1.0+0x19bde7)
#26 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#27 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#28 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#29 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#30 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#31 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#32 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#33 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#34 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#35 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#36 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#37 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#38 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#39 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#40 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#41 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#42 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#43 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#44 0x00007f22b8417905 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19d905)
#45 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#46 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#47 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#48 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#49 0x00007f22b8374d33 PyEval_EvalCode (/lib64/libpython3.6m.so.1.0+0xfad33)
#50 0x00007f22b8482c02 (/lib64/libpython3.6m.so.1.0+0x208c02)
#51 0x00007f22b8484dbd PyRun_StringFlags (/lib64/libpython3.6m.so.1.0+0x20adbd)
#52 0x00007f22b848725c PyRun_SimpleStringFlags (/lib64/libpython3.6m.so.1.0+0x20d25c)
#53 0x00007f22c2b4e216 (/lib64/liblldb.so.12+0xb00216)
#54 0x00007f22c2662fbe (/lib64/liblldb.so.12+0x614fbe)
#55 0x00007f22c274512e (/lib64/liblldb.so.12+0x6f712e)
#56 0x00007f22c22ef2fe lldb::SBDebugger::RunCommandInterpreter(bool, bool) (/lib64/liblldb.so.12+0x2a12fe)
#57 0x000055dc126cd577 (/usr/bin/lldb+0xa577)
#58 0x000055dc126c9ba7 (/usr/bin/lldb+0x6ba7)
#59 0x00007f22b87f6d85 __libc_start_main (/lib64/libc.so.6+0x3ad85)
#60 0x000055dc126c9c1e (/usr/bin/lldb+0x6c1e)
[1]    984562 segmentation fault (core dumped)  lldb

[DavidSpickett]

Didn't realise you'd opened this, closed mine as a dupe.

@medismailben as Python owner.

[llvmbot]

@llvm/issue-subscribers-lldb

When trying to call `pdb.set_trace()` in a script in LLDB, I get an error about the `lldb_editline` module not having the attribute `set_completer_delims`.

polaris ➜  ~  lldb --version
lldb version 12.0.1
polaris ➜  ~  lldb
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> import sys;
>>> sys.executable
'/usr/bin/python3'
>>> sys.version
'3.6.8 (default, Jan 25 2023, 15:03:30) \n[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)]'
>>> import pdb
>>> pdb.set_trace()
Traceback (most recent call last):
  File "/usr/lib64/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "<console>", line 1, in <module>
  File "/usr/lib64/python3.6/pdb.py", line 1585, in set_trace
    Pdb().set_trace(sys._getframe().f_back)
  File "/usr/lib64/python3.6/pdb.py", line 156, in __init__
    readline.set_completer_delims(' \t\n`@#$%^&*()=+[{]}\\|;:\'",<>?')
AttributeError: module 'lldb_editline' has no attribute 'set_completer_delims'

If I run the same version of python from the command line, I get the following:

polaris ➜  ~  python3.6
Python 3.6.8 (default, Jan 25 2023, 15:03:30) 
[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.executable
'/usr/bin/python3.6'
>>> sys.version
'3.6.8 (default, Jan 25 2023, 15:03:30) \n[GCC 8.5.0 20210514 (Red Hat 8.5.0-18)]'
>>> import pdb
>>> pdb.set_trace()
--Return--
> <stdin>(1)<module>()->None
(Pdb) 

If I try to manually load the local readline module, LLDB just seg faults.

polaris ➜  ~  lldb
(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> import importlib.util
>>> import sys
>>> spec = importlib.util.spec_from_file_location("readline", "/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so")
>>> spec
ModuleSpec(name='readline', loader=<_frozen_importlib_external.ExtensionFileLoader object at 0x7f22a63889b0>, origin='/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so')
>>> foo = importlib.util.module_from_spec(spec)
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0.      Program arguments: lldb
 #<!-- -->0 0x00007f22b9fffa00 llvm::sys::PrintStackTrace(llvm::raw_ostream&amp;, int) (/lib64/libLLVM-12.so+0xb4fa00)
 #<!-- -->1 0x00007f22b9ffd5c4 llvm::sys::RunSignalHandlers() (/lib64/libLLVM-12.so+0xb4d5c4)
 #<!-- -->2 0x00007f22b9ffe155 (/lib64/libLLVM-12.so+0xb4e155)
 #<!-- -->3 0x00007f22c34a4cf0 __restore_rt (/lib64/libpthread.so.0+0x12cf0)
 #<!-- -->4 0x00007f22b838aad4 PyModule_GetState (/lib64/libpython3.6m.so.1.0+0x110ad4)
 #<!-- -->5 0x00007f22a556a63d (/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so+0x463d)
 #<!-- -->6 0x00007f22b7264ca5 rl_initialize (/lib64/libedit.so.0+0x1eca5)
 #<!-- -->7 0x00007f22a556aa1d PyInit_readline (/usr/lib64/python3.6/lib-dynload/readline.cpython-36m-x86_64-linux-gnu.so+0x4a1d)
 #<!-- -->8 0x00007f22b8478bd2 _PyImport_LoadDynamicModuleWithSpec (/lib64/libpython3.6m.so.1.0+0x1febd2)
 #<!-- -->9 0x00007f22b8478dd1 (/lib64/libpython3.6m.so.1.0+0x1fedd1)
#<!-- -->10 0x00007f22b840ed92 PyCFunction_Call (/lib64/libpython3.6m.so.1.0+0x194d92)
#<!-- -->11 0x00007f22b841c98d _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x1a298d)
#<!-- -->12 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->13 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#<!-- -->14 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->15 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->16 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#<!-- -->17 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->18 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->19 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#<!-- -->20 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->21 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->22 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->23 0x00007f22b8374d33 PyEval_EvalCode (/lib64/libpython3.6m.so.1.0+0xfad33)
#<!-- -->24 0x00007f22b8484ec0 (/lib64/libpython3.6m.so.1.0+0x20aec0)
#<!-- -->25 0x00007f22b8415de7 (/lib64/libpython3.6m.so.1.0+0x19bde7)
#<!-- -->26 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->27 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#<!-- -->28 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->29 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->30 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->31 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#<!-- -->32 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->33 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->34 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#<!-- -->35 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->36 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->37 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->38 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#<!-- -->39 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->40 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->41 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->42 0x00007f22b83f3b80 (/lib64/libpython3.6m.so.1.0+0x179b80)
#<!-- -->43 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->44 0x00007f22b8417905 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19d905)
#<!-- -->45 0x00007f22b83f3998 (/lib64/libpython3.6m.so.1.0+0x179998)
#<!-- -->46 0x00007f22b8416087 (/lib64/libpython3.6m.so.1.0+0x19c087)
#<!-- -->47 0x00007f22b8416cd8 _PyEval_EvalFrameDefault (/lib64/libpython3.6m.so.1.0+0x19ccd8)
#<!-- -->48 0x00007f22b8373994 (/lib64/libpython3.6m.so.1.0+0xf9994)
#<!-- -->49 0x00007f22b8374d33 PyEval_EvalCode (/lib64/libpython3.6m.so.1.0+0xfad33)
#<!-- -->50 0x00007f22b8482c02 (/lib64/libpython3.6m.so.1.0+0x208c02)
#<!-- -->51 0x00007f22b8484dbd PyRun_StringFlags (/lib64/libpython3.6m.so.1.0+0x20adbd)
#<!-- -->52 0x00007f22b848725c PyRun_SimpleStringFlags (/lib64/libpython3.6m.so.1.0+0x20d25c)
#<!-- -->53 0x00007f22c2b4e216 (/lib64/liblldb.so.12+0xb00216)
#<!-- -->54 0x00007f22c2662fbe (/lib64/liblldb.so.12+0x614fbe)
#<!-- -->55 0x00007f22c274512e (/lib64/liblldb.so.12+0x6f712e)
#<!-- -->56 0x00007f22c22ef2fe lldb::SBDebugger::RunCommandInterpreter(bool, bool) (/lib64/liblldb.so.12+0x2a12fe)
#<!-- -->57 0x000055dc126cd577 (/usr/bin/lldb+0xa577)
#<!-- -->58 0x000055dc126c9ba7 (/usr/bin/lldb+0x6ba7)
#<!-- -->59 0x00007f22b87f6d85 __libc_start_main (/lib64/libc.so.6+0x3ad85)
#<!-- -->60 0x000055dc126c9c1e (/usr/bin/lldb+0x6c1e)
[1]    984562 segmentation fault (core dumped)  lldb

[JDevlieghere]

The lldb_editline module is a workaround for a crash caused by loading both libedit (lldb) and readline(python) in the same process. @labath created this simple readline wrapper that uses editline instead of readline. The problem here is that PDB assumes that the module has certain methods, which we don't implement.

Probably the easiest solution here is to add empty shims for the methods that PDB expects. But unless we do this for all the methods provided by Python's readline module, we can expect similar bug reports from other packages.

PS: The original bug was fixed by allowing you to build Python against libedit. That doesn't really solve our issues though, because we link against the system Python rather than vendoring our own copy. There's probably a way to check which of the two Python was built against and avoid the workaround, but I don't see why Python on Linux would use editline instead of readline.

[lambdaknight]

Could it be re-implemented so that lldb just uses whatever Python is linked against?