[New-bugs-announce] [issue40019] test_gdb should better detect when Python is optimized

[STINNER Victor]

New submission from STINNER Victor <vstinner at python.org>:

On my PR 19077 which changes Python/ceval.c, test_gdb fails on Travis CI with Python compiled with clang -Og.

The -Og optimization level is a compromise between performance and the ability to debug Python. The problem is that gdb fails to retrieve some information and so test_gdb fails.

I proposed bpo-38350 "./configure --with-pydebug should use -O0 rather than -Og", but the status quo is to continue to use -Og by default.

See examples of test_gdb failures from PR 19077 below.

I propose to skip a test if one of the follow pattern is found in gdb output:

* '<optimized out>',
* '(frame information optimized out)',
* 'Unable to read information on python frame',

======================================================================
FAIL: test_basic_command (test.test_gdb.PyListTests)
Verify that the "py-list" command works
----------------------------------------------------------------------
(...)

AssertionError: (...)

'Breakpoint 1 at 0x5aabf1: file Python/bltinmodule.c, line 1173.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, builtin_id (self=, v=42) at Python/bltinmodule.c:1173
1173\t    PyObject *id = PyLong_FromVoidPtr(v);
Unable to read information on python frame
'

did not end with

'   5
   6    def bar(a, b, c):
   7        baz(a, b, c)
   8
   9    def baz(*args):
 >10        id(42)
  11
  12    foo(1, 2, 3)
'


======================================================================
FAIL: test_bt (test.test_gdb.PyBtTests)
Verify that the "py-bt" command works
----------------------------------------------------------------------
(...)
AssertionError:

'Breakpoint 1 at 0x5aabf1: file Python/bltinmodule.c, line 1173.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, builtin_id (self=, v=42) at Python/bltinmodule.c:1173
1173\t    PyObject *id = PyLong_FromVoidPtr(v);
Traceback (most recent call first):
  <built-in method id of module object at remote 0x7ffff7f87050>
  (frame information optimized out)
  File "/home/travis/build/python/cpython/Lib/test/gdb_sample.py", line 7, in bar
    baz(a, b, c)
  File "/home/travis/build/python/cpython/Lib/test/gdb_sample.py", line 4, in foo
    bar(a, b, c)
  (frame information optimized out)
'

did not match

'^.*
Traceback \\(most recent call first\\):
  <built-in method id of module object .*>
  File ".*gdb_sample.py", line 10, in baz
    id\\(42\\)
  File ".*gdb_sample.py", line 7, in bar
    baz\\(a, b, c\\)
  File ".*gdb_sample.py", line 4, in foo
    bar\\(a, b, c\\)
  File ".*gdb_sample.py", line 12, in <module>
    foo\\(1, 2, 3\\)
'

----------
components: Tests
messages: 364640
nosy: vstinner
priority: normal
severity: normal
status: open
title: test_gdb  should better detect when Python is optimized
versions: Python 3.9

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40019>
_______________________________________