[bug] 'compiled-objects-have-debug-symbols' false positive on mach-o files that have been passed through 'strip'

[jameslamb]

What did you expect to happen?

Expected compiled-objects-have-debug-symbols check to only find debug symbols if a mach-o binary contains them.

What actually happened?

Over in LightGBM, observed that when upgrading scikit-build-core for a shared library from v0.4.4 to 0.9.3, pydistcheck started raising this on the resulting library lib_lightgbm.dylib.

1. [compiled-objects-have-debug-symbols] Found compiled object containing debug symbols. For details, extract the distribution contents and run 'nm -a "lightgbm/lib/lib_lightgbm.dylib"'.
errors found while checking: 1

But ONLY that macOS library... not the equivalent files on linux (lib_lightgbm.so) or windows (lib_lightgbm.dll).

How can someone else reproduce this problem?

I mention that scikit-build-core version because in that range, scikit-build-core added the ability to strip the binaries it produced.

https://github.com/scikit-build/scikit-build-core/blob/2994db5d993f0cb252dbeebfac7d66677b670ed8/README.md#L278-279

I built that library (lib_lightgbm.dylib) on an M2 mac, in a build driven by scikit-build-core, like this:

git clone \
    --recursive \
    [email protected]:microsoft/LightGBM.git \
    /tmp/lightgbm

cd /tmp/lightgbm
sh build-python.sh bdist_wheel
unzip -d ./tmp ./dist/*.whl
nm ./lightgbm/lib/lib_lightgbm.dylib > o.txt
nm -a ./lightgbm/lib/lib_lightgbm.dylib > a.txt

Then diffed those files. Only saw 1 difference.

The results of nm -a includes this:

0000000005614542 - 00 0000   OPT radr://5614542

It seems that maybe this is added by strip?

I found this repo, https://github.com/nico/lssym, which says

(Compare with the output of `nm lssym` and `dsymutil -s lssym` in both cases.
Note that `strip` adds a symbol that looks like

    radr://5614542    N_STAB 3c    n_sect 000 n_desc 0x0000    n_value 0x5614542

I wonder what that bug is. `nm` doesn't list it because `nm` only lists symbols,
and this is a stabs debug info entry which `nm` only shows if you pass `-a`.)

I strongly suspect that's what's happening here! Not sure what the best fix is though for pydistcheck, will need to think through that.

What version of pydistcheck are you using?

0.6.0

Notes

Thanks @nico for putting up https://github.com/nico/lssym! It was a great clue to help me investigate this!!