Debug symbols not available despite following manual

[vandenoever]

Issue description

I'd like to debug an application on NixOS. The application crashes in libQt5Script.so.5 from the package qtscript. I've looked at the manual for adding debug symbols.

Simply adding environment.enableDebugInfo = true does not give me the debug symbols.

A second attempt is to use packageOverrides. I've explicitly put separateDebugInfo = true; in the qtscript package. But it still does not let nixos-rebuild install any debug info.

This is the relevant fragment from /etc/nixos/configuration.nix:

  environment.enableDebugInfo = true;
  nixpkgs.config.packageOverrides = pkgs: {
    qt5 = pkgs.qt5 // {
      qtscript = pkgs.qt5.qtscript.overrideAttrs (attrs: {
        separateDebugInfo = true;
      });
    };
    qt511 = pkgs.qt511 // {
      qtscript = pkgs.qt511.qtscript.overrideAttrs (attrs: {
        separateDebugInfo = true;
      });
    };
  };

Technical details

 - system: `"x86_64-linux"`
 - host os: `Linux 4.18.20, NixOS, 18.09.1636.b144dfa3b27 (Jellyfish)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.1.3`
 - channels(root): `"nixos-18.09.1636.b144dfa3b27"`
 - channels(oever): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[symphorien]

The separate debug files provided for qtscript are empty shells containing no actual debug symbols.

$  tree -as /nix/store/ix8vc9krrsajbfn2rcn118hgr2g0f9vw-qtscript-5.11.1-debug/lib/debug                          
/nix/store/ix8vc9krrsajbfn2rcn118hgr2g0f9vw-qtscript-5.11.1-debug/lib/debug
├── [       4096]  .build-id
│   ├── [       4096]  8c
│   │   └── [       2680]  f0d4a5c60e629b4c9b241539710e5e9e9bd1de.debug
│   └── [       4096]  f0
│       └── [       2680]  b975465eef50ed3be72bf9d6a697f44e8fc1d9.debug
├── [         57]  libQt5Script.so.5.11.1 -> .build-id/8c/f0d4a5c60e629b4c9b241539710e5e9e9bd1de.debug
└── [         57]  libQt5ScriptTools.so.5.11.1 -> .build-id/f0/b975465eef50ed3be72bf9d6a697f44e8fc1d9.debug

Probably qtScrip's build system already strips the libs aggressively before the fixupPhase saves the debug info in the separate output ?

[symphorien]

Also maybe you will find this article of interest: https://nixos.wiki/wiki/Debug_Symbols

[vandenoever]

The Debug_Symbols article has educated me some.

I've tried to read the derivation for the QtScript on my system, but it's missing:

$ realpath "$(type -P "kmail")"
/nix/store/37angcmf0npkfxa3m7rr988na52pcln1-kmail-18.08.0/bin/kmail
$ ldd /nix/store/37angcmf0npkfxa3m7rr988na52pcln1-kmail-18.08.0/bin/kmail | grep qtscript
        libQt5Script.so.5 => /nix/store/vk1ifz8540zrzchs93y6z07wfxmwh62k-qtscript-5.11.1/lib/libQt5Script.so.5 (0x00007f41e994f000)
$ nix-store --query --deriver /nix/store/vk1ifz8540zrzchs93y6z07wfxmwh62k-qtscript-5.11.1/
/nix/store/92jkrjd1hx2df3l4c2mvdwgirj95cn8v-qtscript-5.11.1.drv
$ ls /nix/store/92jkrjd1hx2df3l4c2mvdwgirj95cn8v-qtscript-5.11.1.drv
ls: cannot access '/nix/store/92jkrjd1hx2df3l4c2mvdwgirj95cn8v-qtscript-5.11.1.drv': No such file or directory

[symphorien]

afaik derivations don't always live on disk, sometimes they are only in the nix database. Does nix show-derivation still work ?
In any case, you can probably download the .drv from the cache with nix copy.

[stale]

Thank you for your contributions.

This has been automatically marked as stale because it has had no activity for 180 days.

If this is still important to you, we ask that you leave a comment below. Your comment can be as simple as "still important to me". This lets people see that at least one person still cares about this. Someone will have to do this at most twice a year if there is no other activity.

Here are suggestions that might help resolve this more quickly:

1. Search for maintainers and people that previously touched the related code and @ mention them in a comment.
2. Ask on the NixOS Discourse.
3. Ask on the #nixos channel on irc.freenode.net.

[waldheinz]

I think the problem is that environment.enableDebugInfo pulls in debug info only for packages that are directly listed in environment.systemPackages, not their dependencies.

So having separateDebugInfo = true on a lib causes the debug output to be built, but because nobody lists a lib in systemPackages, the enableDebugInfo flag does not cause that output to be pulled in. Listing a lib in systemPackages causes the debug info to be available. I just verified this for another lib because I did not want to wait for qt to compile.

Following the code through debug-info.nix, system-path.nix and finally buildenv/default.nix shows that this is what happens.

The documentation for environment.enableDebugInfo is not explicit if this is the intended behavior, but it sure came as a surprise for me just like @vandenoever .

[stale]

I marked this as stale due to inactivity. → More info