Investigating crash on feature/igc

[bhankas]

Thank you for allowing builds from feature/igc. I have been trying out the build for past couple of days and have encountered couple of crashes during touchpad/cursor use. I opened a bug on bug-gnu-emacs (75895), and one of the developers would like to ask some questions:

1. does the emacs build generate debug information needed to interpret
   core files? If so, how do we get at it, both when running Nix and when
   not running Nix? ("debuginfod" support, maybe? Note that debuginfod is
   very bad at the second part, but it's better than nothing).

2. Can we associate the emacs binary and the emacs.pdmp file with core
   dumps? it's hard to interpret crashes without all three files.

3. Have you run into any problems with reproducible builds yet? Emacs
   builds aren't reproducible for a number of reasons, so it may be good to
   be in contact about those, if reproducibility is still a goal there.

4. Is there a good way to review the build instructions? I don't read
   .nix files but I could probably learn to :-)

5. Is ASLR in use?

6. Most importantly, how widely available is this? New testers for
   feature/igc are desperately needed, and if this helps us gain even a few
   of those that would be wonderful! Thank you so much for that work!

7. Can we add instructions to test on Nix to our documentation? While
   docker is problematic, I end up using it, and if there were an easy way
   to test feature/igc using nix and docker, that would help a lot.

8. Which architectures do you support?

I'm not fully informed to answer them hence posting here.

In particular, we'd like to build emacs on feature/igc branch with pgtk and with debug symbols attached so the coredump after crash is actually useful. As it is, current coredump is pretty useless for getting useful stacktrace.

I understand this may not be ideal place to ask these questions, and will be happy to take them elsewhere (matrix has never really worked well for me, so I did not post there).

[jian-lin]

Some questions, such as debug info, reproducible builds and ASLR ones, are not nix-emacs-specific, they are nix-specific. So you are more likely to be helped if you post them at https://matrix.to/#/#nix:nixos.org or https://discourse.nixos.org/.

Some info about nix-related debug info:

• https://nixos.org/manual/nixpkgs/unstable/#stdenv-separateDebugInfo
• https://wiki.nixos.org/wiki/Debug_Symbols

I think reproducible builds is one goal of nix. You can find more info here: https://reproducible.nixos.org/. There is also a matrix room: https://matrix.to/#/#reprocible-builds:nixos.org.

Emacs-related nix files are under pkgs/applications/editors/emacs/. The call link is default.nix -> sources.nix -> make-emacs.nix. make-emacs.nix is the main file. This emacs-overlay provides two igc builds by changing the build recipe of Emacs in Nixpkgs.

We have pre-built cache for x86_64-linux and aarch64-linux for igc emacs. You can build it from source on darwin (and probably more) systems.

[pipcet]

@bhankas Thanks for posting this!

I think it's great to make feature/igc available for more people to test, but as a non-Nix user, I may need some help debugging problems with such builds. Last I looked, debuginfod was a bit problematic to work with even on more` standardized distributions.

Maybe the best course of action here is to wait for a few more bug reports and see whether we can work out how to debug them?

Open to suggestions, and thanks for the responses so far :-)