Compiling python with enableDebugging and KeepDebuggingInfo results in no debug symbols

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1

I want to use gdb to debug Cython code, and am running into an early roadblock: gdb can’t find python’s symbols, even when compiled so that they should be present.

The definition of the python I’m debugging is

pythonOverlay = self: super: {
    python38  = ((enableDebugging super.python38).override {
    packageOverrides = myPackageOverrides;
    }).overrideAttrs (oldAttrs: {
        keepDebugInfo = true;
        disallowedReferences = [];
        });
  };

Yet, when I run "gdb " I get

[henry@bollum:~/Projects/eyeserver/dserver/src]$ ./debugPython2.sh 
GNU gdb (GDB) 10.1
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License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
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There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-unknown-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
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    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
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Reading symbols from /nix/store/wkw6fsjasr7jbbrlakxxpbiapa8hws42-python3-3.8.7/bin/python...
(No debugging symbols found in /nix/store/wkw6fsjasr7jbbrlakxxpbiapa8hws42-python3-3.8.7/bin/python)
Starting program: /nix/store/wkw6fsjasr7jbbrlakxxpbiapa8hws42-python3-3.8.7/bin/python 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/nix/store/gafigwfaimlziam6qhw1m8dz4h952g1n-glibc-2.32-35/lib/libthread_db.so.1".
Python 3.8.7 (default, Dec 21 2020, 17:18:55) 
[GCC 10.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

[Inferior 1 (process 23057) exited normally]
(gdb) (gdb) 
quit

the contents of my debug script are as follows

#! /nix/store/can00lfiynqkbsdkkmgp6qg8p8w92cxa-bash-4.4-p23/bin/bash -e
export PYTHONHOME='/nix/store/2c5hpk7i7s87vqd6q743a6lqccz52342-python3-3.8.7-env'
export PYTHONNOUSERSITE='true'
gdb -ex=r --args "/nix/store/wkw6fsjasr7jbbrlakxxpbiapa8hws42-python3-3.8.7/bin/python"  "${extraFlagsArray[@]}" "$@"

while the wrapper that (/home/henry/.nix-profile/bin/python) runs python (forcing the script) is

#! /nix/store/cwnwyy82wrq53820z6yg7869z8dl5s7g-bash-4.4-p23/bin/bash -e
export NIX_PYTHONPREFIX='/nix/store/2c5hpk7i7s87vqd6q743a6lqccz52342-python3-3.8.7-env'
export NIX_PYTHONEXECUTABLE='/nix/store/2c5hpk7i7s87vqd6q743a6lqccz52342-python3-3.8.7-env/bin/python3.8'
export NIX_PYTHONPATH='/nix/store/2c5hpk7i7s87vqd6q743a6lqccz52342-python3-3.8.7-env/lib/python3.8/site-packages'
export PYTHONNOUSERSITE='true'
exec "/nix/store/wkw6fsjasr7jbbrlakxxpbiapa8hws42-python3-3.8.7/bin/python"  "$@"
2

Have you tried dontStrip = true?

(Debug Symbols - NixOS Wiki)

1 Like
3

Wonder if this is a usecase for GitHub - edolstra/dwarffs: A FUSE filesystem that allows tools like gdb to look up debug info files via HTTP.

4

I’ve tried a couple of suggestions:

  1. Using dontStrip in addition to the other options
  2. Using python38Full rather than python38

Both result in the same baffling error message: conflicting versions of the ‘six’ library.
Makes sense – until I remember that I’m using an overlay to override all python38 in the build.
Since I’m doing this in home-manager, apparently I lose access to show-trace or any other debugging tool, requiring me to fix it with my macho eyeballing skills. Which aren’t up to the task. Is there any way to figure out who is pulling in each given version of six that contribute to the conflict?

5

It seems like it. I think I’d have to convert my system to using flakes to take advantage of it, though.