https://buildbot.python.org/all/#/builders/727

test_tuples (test.test_gdb.PrettyPrintTests)
Verify the pretty-printing of tuples ... ok
test_bt (test.test_gdb.PyBtTests)
Verify that the "py-bt" command works ... FAIL
Stderr:
Python Exception <class 'gdb.MemoryError'> Cannot access memory at address 0xfffffedc: 
Error occurred in Python command: Cannot access memory at address 0xfffffedc

and a pile of similar errors after test_bt

Marking release blocker as this isn't present in 3.8 or earlier, we've got a regression here.

i haven't tried to debug yet, but that pointer value smells like something did a negative offset from NULL...

Some data from a recent build:
https://buildbot.python.org/all/#/builders/645/builds/480

That's 32-bit ARM, armv7l ABI with GCC 8.3 and GDB 8.2.

Python is built with -Og optimization level. In my experience, gdb fails to read debug symbols when Python is optimized at -Og level. Last time I asked a gdb developer, he told me that he always use -O0, so do I.


test.pythoninfo:

platform.architecture: 32bit ELF
platform.libc_ver: glibc 2.28
platform.platform: Linux-4.19.97-v7l+-armv7l-with-glibc2.28
platform.python_implementation: CPython

CC.version: gcc (Raspbian 8.3.0-6+rpi1) 8.3.0
sysconfig[PY_CFLAGS]: -Wno-unused-result -Wsign-compare -g -Og -Wall
sysconfig[PY_CFLAGS_NODIST]: -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal
sysconfig[PY_STDMODULE_CFLAGS]: -Wno-unused-result -Wsign-compare -g -Og -Wall -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal -I. -I./Include

gdb_version: GNU gdb (Raspbian 8.2.1-2) 8.2.1

> Marking release blocker as this isn't present in 3.8 or earlier, we've got a regression here.

FYI we have issue with test_gdb on Fedora for at least 5 years. Most issues come from -Og optimization level of test_gdb.

Recently, I modified test_gdb to skip tests when we detect that gdb fails to read debug symbols, which happens often when using -Og: bpo-40019.

commit 7bf069b6110278102c8f4719975a5eb5a5af25f9
Author: Victor Stinner <vstinner@python.org>
Date:   Fri Mar 20 08:23:26 2020 +0100

    bpo-40019: Skip test_gdb if Python was optimized (GH-19081)
    
    test_gdb now skips tests if it detects that gdb failed to read debug
    information because the Python binary is optimized.

I closed bpo-17737 "test_gdb fails on armv7hl" as out of date.

This will miss 3.9.0b4.

Note: 3.9.0b5, the last beta before 3.9.0, is next week.

gdb doesn't work fully when Python is built with -Og. I don't think that there is much that we can do. I suggest to skip test_gdb on 32-bit ARM when Python is built with -Og.

I don't think that this regular requires the "release blocker" priority. It would be nice to fix but it should not hold the 3.9.0 final release.

Downgrading since this missed rc1 anyway.