Glibc Dynamic Linking issue

This repository contains a proposed fix for jetify-com/devbox#1276

Problem

The original devbox.json was:

{
  "packages": [
    "python310@latest",
    "python310Packages.pip@latest",
    "[email protected]",
    "[email protected]",
    "[email protected]",
    "xorg.xorgserver@latest",
    "[email protected]",
    "[email protected]",
    "stdenv.cc.cc.lib",
    "[email protected]"
  ],
  "shell": {
    "init_hook": [
      ". $VENV_DIR/bin/activate",
      "pip install -q -r requirements.txt"
    ]
  },
  "nixpkgs": {
    "commit": "a16f7eb56e88c8985fcc6eb81dabd6cade4e425a"
  }
}

It also has this requirements.txt:

Sphinx==5.3.0
sphinx_rtd_theme==1.1.1
sphinxcontrib-plantuml==0.25
sphinxcontrib-svg2pdfconverter==1.2.1
sphinxcontrib-drawio==0.0.16
sphinxcontrib-bibtex==2.5.0
Pillow==9.3.0
matplotlib==3.7.2

and main.py:

import matplotlib

def main():
    print("hello world")

main()

However, running python main.py gives this error:

Traceback (most recent call last):
  File "/code/main.py", line 1, in <module>
    import matplotlib
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/__init__.py", line 129, in <module>
    from . import _api, _version, cbook, _docstring, rcsetup
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/rcsetup.py", line 27, in <module>
    from matplotlib.colors import Colormap, is_color_like
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/colors.py", line 56, in <module>
    from matplotlib import _api, _cm, cbook, scale
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/scale.py", line 22, in <module>
    from matplotlib.ticker import (
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/ticker.py", line 138, in <module>
    from matplotlib import transforms as mtransforms
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/transforms.py", line 49, in <module>
    from matplotlib._path import (
ImportError: libstdc++.so.6: cannot open shared object file: No such file or directory

Here, matplotlib requires a libstdc++.so.6 library.

The usual fix: stdenv.cc.cc.lib

In the nix and Devbox communities, the usual suggestion to fix this is devbox add stdenv.cc.cc.lib.

However, doing this leads to two errors now:

$ python main.py
Traceback (most recent call last):
  File "/code/main.py", line 1, in <module>
    import matplotlib
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/__init__.py", line 129, in <module>
    from . import _api, _version, cbook, _docstring, rcsetup
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/rcsetup.py", line 27, in <module>
    from matplotlib.colors import Colormap, is_color_like
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/colors.py", line 56, in <module>
    from matplotlib import _api, _cm, cbook, scale
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/scale.py", line 22, in <module>
    from matplotlib.ticker import (
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/ticker.py", line 138, in <module>
    from matplotlib import transforms as mtransforms
  File "/code/.devbox/virtenv/python310Packages.pip/.venv/lib/python3.10/site-packages/matplotlib/transforms.py", line 49, in <module>
    from matplotlib._path import (
ImportError: /nix/store/lqz6hmd86viw83f9qll2ip87jhb7p1ah-glibc-2.35-224/lib/libc.so.6: version `GLIBC_2.36' not found (required by /code/.devbox/nix/profile/default/lib/libstdc++.so.6)

and

$ rsvg-convert --help
/nix/store/0ccn204v5kds9i08x7plf4x644l6wm87-librsvg-2.52.5/bin/rsvg-convert: /nix/store/4s21k8k7p1mfik0b33r2spq5hq7774k1-glibc-2.33-108/lib/libc.so.6: version `GLIBC_2.35' not found (required by /code/.devbox/nix/profile/default/lib/libgcc_s.so.1)
/nix/store/0ccn204v5kds9i08x7plf4x644l6wm87-librsvg-2.52.5/bin/rsvg-convert: /nix/store/4s21k8k7p1mfik0b33r2spq5hq7774k1-glibc-2.33-108/lib/libc.so.6: version `GLIBC_2.34' not found (required by /code/.devbox/nix/profile/default/lib/libgcc_s.so.1)

This is happening because the libstdc++.so.6 and libgcc_s.so.1 libraries are expecting newer versions of glibc than python3 and rsvg-convert were packaged with.

New fix: patch python310 and librsvg to use latest glibc

In this fix, the devbox.json is now:

{
  "packages": [
    "path:./local-flakes/python",
    "python310Packages.pip@latest",
    "[email protected]",
    "path:./local-flakes/librsvg",
    "xorg.xorgserver@latest",
    "[email protected]",
    "[email protected]",
    "[email protected]",
    "github:nixos/nixpkgs/7131f3c223a2d799568e4b278380cd9dac2b8579#stdenv.cc.cc.lib"
  ],
  "shell": {
    "init_hook": [
      ". $VENV_DIR/bin/activate",
      "pip install -q -r requirements.txt"
    ]
  },
  "nixpkgs": {
    "commit": "a16f7eb56e88c8985fcc6eb81dabd6cade4e425a"
  }
}

You'll notice three changes:

1. path:./local-flakes/python
2. path:./local-flakes/librsvg
3. github:nixos/nixpkgs/7131f3c223a2d799568e4b278380cd9dac2b8579#stdenv.cc.cc.lib

First, within local-flakes/python, we patch python3 to use the latest glibc

 python3 = wrapper.libcPatcher pkgs-latest "python-patched" pkgs-python.python3;

This uses a small nix function libcPatcher that is essentially a bash-script. This bash-script uses a utility called patchelf to ensure that python3 will execute with the latest libc. I'll add details to the readme of https://github.com/savil/libc-patcher to explain what it does internally.

Second, path:./local-flakes/librsvg does the very same operation as the python flake.

Lastly, regarding github:nixos/nixpkgs/7131f3c223a2d799568e4b278380cd9dac2b8579#stdenv.cc.cc.lib: The nixpkgs commit hash here must match that of the nixpkgs-latest in the python and librsvg flakes from which the libc is used.

Starting a devbox shell with this devbox.json and these local flakes, gives:

# may need to clear local state
> rm -rf .devbox

> devbox shell
Starting a devbox shell...

(devbox) $ python main.py
hello world

(devbox)$ rsvg-convert --help
rsvg-convert version 2.52.5
... // omitted

This seems to now work!

NOTE: the flake.nix in the local-flake folders have a hardcoded system = x86_64-linux; in them. If you'd like to try this out on another architecture, then please modify this value. Nix supports these systems. This libc issue doesn't apply to MacOS, since Nix's stdenv uses clang on Macs instead of libc.

Reasoning and Limitations

This fix relies on the following assumptions and observations:

1. Glibc has a high level of backwards-compatibility. This lets us patch binaries to use newer glibc versions than they were initially built with. However, it is not perfectly backwards compatible, so this may yet fail in some scenarios. Glibc also has some private symbols GLIBC_PRIVATE, which are not backwards compatible.
2. This only patches Glibc, and not other libraries. That said, Glibc seems to be the most (only?) frequently reported library incompatibility reported by Devbox users.