cpython: don't use lchmod() on Linux, fix w/musl #39517
Merged
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upstream issue:
https://bugs.python.org/issue31940
There are two PR's proposed to fix this,
but both seem to be stalling waiting for review.
I previously used what appears to be the favored
of the two approaches[1] to fix this,
with plan of keeping it musl-only until PR was merged.
However, while writing up a commit message
explaining the problem and why it needed fixing...
I investigated a bit and found it increasingly
hard to justify anything other than ...
simply not using lchmod.
Here's what I found:
with fchmodat(), which AFAICT is generally preferred.
electing instead to use lchmod() behavior
as a proxy for whether fchmodat() "works".
I'm not sure I follow their reasoning...
and so returns EOPNOTSUPP "op not supported"
since it's not valid on BSD's lchmod.
instead checks for glibc preprocessor defines
to indicate if the function is just a stub[3];
somewhat fittingly, if the magic macros are defined
then the next line of the C source is "choke me",
causing the compiler to trip, fall, and point
a finger at whatever is near where it ends up.
(somewhat amusing, but AFAIK effective way to get an error :P)
I'm leaving out links to threads on mailing lists and such,
but for now I hope I've convinced you
(or to those reading commit history: explained my reasons)
that this is a bit of a mess[4].
And so instead of making a big mess messier,
and with hopes of never thinking about this again,
I propose we simply tell Python "don't use lchmod" on Linux.
[1] python/cpython#4783
[2] https://github.com/python/cpython/blob/28453feaa8d88bbcbf6d834b1d5ca396d17265f2/Lib/os.py#L144
[3] https://github.com/python/cpython/blob/28453feaa8d88bbcbf6d834b1d5ca396d17265f2/configure#L2198
[4] Messes happen, no good intention goes unpunished :).
(I've tested on a slightly different branch, let's see what borg says)
build-use-sandbox
innix.conf
on non-NixOS)nix-shell -p nox --run "nox-review wip"
./result/bin/
)