configd is an alias for the SystemConfiguration framework, which is now
always part of the SDK. Removing this parameter because it effectively
does nothing now, which could be misleading to users.
In preparation for the deprecation of `stdenv.isX`.
These shorthands are not conducive to cross-compilation because they
hide the platforms.
Darwin might get cross-compilation for which the continued usage of `stdenv.isDarwin` will get in the way
One example of why this is bad and especially affects compiler packages
https://www.github.com/NixOS/nixpkgs/pull/343059
There are too many files to go through manually but a treewide should
get users thinking when they see a `hostPlatform.isX` in a place where it
doesn't make sense.
```
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv.is" "stdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv'.is" "stdenv'.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "clangStdenv.is" "clangStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "gccStdenv.is" "gccStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenvNoCC.is" "stdenvNoCC.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "inherit (stdenv) is" "inherit (stdenv.hostPlatform) is"
fd --type f "\.nix" | xargs sd --fixed-strings "buildStdenv.is" "buildStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "effectiveStdenv.is" "effectiveStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "originalStdenv.is" "originalStdenv.hostPlatform.is"
```
In the past I was very active with Python packaging.
For several years now I was hardly around as maintainer,
so it does not make sense I am listed as a maintainer for
these makes. Looking back, I should have removed myself
as maintainer already much longer ago. Anyway, better late
than never.
It's been a fun ride, and I do intend to occasionally contribute
to Nixpkgs, but not in the same way it once was.
The way we build python environments is subtly broken. A python
environment should be semantically identical to a vanilla Python
installation in, say, /usr/local. The current implementation, however,
differs in two important ways. The first is that it's impossible to use
python packages from the environment in python virtual environments. The
second is that the nix-generated environment appears to be a venv, but
it's not.
This commit changes the way python environments are built:
* When generating wrappers for python executables, we inherit argv[0]
from the wrapper. This causes python to initialize its configuration
in the environment with all the correct paths.
* We remove the sitecustomize.py file from the base python package.
This file was used tweak the python configuration after it was
incorrectly initialized. That's no longer necessary.
The end result is that python environments no longer appear to be venvs,
and behave more like a vanilla python installation. In addition it's
possible to create a venv using an environment and use packages from
both the environment and the venv.
with structuredAttrs lists will be bash arrays which cannot be exported
which will be a issue with some patches and some wrappers like cc-wrapper
this makes it clearer that NIX_CFLAGS_COMPILE must be a string as lists
in env cause a eval failure
Without `--with-system-{ffi,expat}` flags, Python will use its own
embedded libraries that are out-of-date. Thanks to it, they can be a
security issue. So let's use our own libraries instead.
This is already what Python 3.x does, so should be safe.
This PR strips down the modified `python27` derivation used by `resholve`. The
idea is to reduce the possible security issues, and also to make it easier to
bootstrap.
ActiveState is a company that is maintaining a fork of Python 2 to fixes
its security issues. Their support is paid, however the code is
open-source. See the details here:
https://www.activestate.com/products/python/python-2-end-of-life-security-updates/
This enable us to drop a bunch of CVE's patches for Python 2.7 and also
it should be easier to maintain, since we can just bump the version once
ActiveState tags a new version.
Python package sets can be overridden by overriding an interpreter
and passing in `packageOverrides = self: super: {...};`. This is fine
in case you need a single interpreter, however, it does not help you
when you want to override all sets.
With this change it is possible to override all sets at once by
appending a list of "extensions" to `pythonPackagesExtensions`.
From reading the implementation you might wonder why a list is used, and
not
`lib.composeExtensions`? The reason is the latter requires knowledge of
the library function. This approach should be easier for most users
as it is similar to how we append to lists of e.g. inputs or patches
when overriding a derivation.
In 9d03ff5222 I made the CPython builds
reproducible. This required not generating default unoptimized bytecode.
I was under the impression the optimized bytecode would be used then,
but you need to opt-in on that. Not having the default bytecode resulted
in a significant performance hit. Therefore, bytecode is generated again
in this commit, and thereby the builds are no longer reproducible.
https://bugs.python.org/issue29708
From the archive `python-gentoo-patches-2.7.18_p8.tar.xz` found at
https://dev.gentoo.org/~mgorny/dist/python/, I copied
`0024-3.6-bpo-42967-only-use-as-a-query-string-separator-G.patch`.
The issue manifests itself as the following on `aarch64-darwin`:
```
>>> import ctypes
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/nix/store/i8cq0xrjirz1rcp65wzcyhj6ypzlw9il-python3-3.7.10/lib/python3.7/ctypes/__init__.py", line 551, in <module>
_reset_cache()
File "/nix/store/i8cq0xrjirz1rcp65wzcyhj6ypzlw9il-python3-3.7.10/lib/python3.7/ctypes/__init__.py", line 273, in _reset_cache
CFUNCTYPE(c_int)(lambda: None)
MemoryError
```
The commit we backport is included in Python 3.8, and it reverts
the change that was introduced all the way back in Python 2.7.
Thanks to the Gentoo team maintaining a fork of python2¹ we can easily
apply their backported patch for this security vulnerability.
[1] https://gitweb.gentoo.org/fork/cpython.git/
As part of the splicing the build/host/target combinations of the interpreter
need to be passed around internally. The chosen names were not very clear,
implying they were package sets whereas actually there were derivations.
Also, don't use autoreconfHook on Darwin with Python 3.
Darwin builds are still impure and fail with
ld: warning: directory not found for option '-L/nix/store/6yhj9djska835wb6ylg46d2yw9dl0sjb-configd-osx-10.8.5/lib'
ld: warning: directory not found for option '-L/nix/store/6yhj9djska835wb6ylg46d2yw9dl0sjb-configd-osx-10.8.5/lib'
ld: warning: object file (/nix/store/0lsij4jl35bnhqhdzla8md6xiswgig5q-Libsystem-osx-10.12.6/lib/crt1.10.6.o) was built for newer OSX version (10.12) than being linked (10.6)
DYLD_LIBRARY_PATH=/private/tmp/nix-build-python3-3.8.3.drv-0/Python-3.8.3 ./python.exe -E -S -m sysconfig --generate-posix-vars ;\
if test $? -ne 0 ; then \
echo "generate-posix-vars failed" ; \
rm -f ./pybuilddir.txt ; \
exit 1 ; \
fi
/nix/store/dsb7d4dwxk6bzlm845z2zx6wp9a8bqc1-bash-4.4-p23/bin/bash: line 5: 72015 Killed: 9 DYLD_LIBRARY_PATH=/private/tmp/nix-build-python3-3.8.3.drv-0/Python-3.8.3 ./python.exe -E -S -m sysconfig --generate-posix-vars
generate-posix-vars failed
make: *** [Makefile:592: pybuilddir.txt] Error 1
I took a close look at how Debian builds the Python interpreter,
because I noticed it ran substantially faster than the one in nixpkgs
and I was curious why.
One thing that I found made a material difference in performance was
this pair of linker flags (passed to the compiler):
-Wl,-O1 -Wl,-Bsymbolic-functions
In other words, effectively the linker gets passed the flags:
-O1 -Bsymbolic-functions
Doing the same thing in nixpkgs turns out to make the interpreter
run about 6% faster, which is quite a big win for such an easy
change. So, let's apply it.
---
I had not known there was a `-O1` flag for the *linker*!
But indeed there is.
These flags are unrelated to "link-time optimization" (LTO), despite
the latter's name. LTO means doing classic compiler optimizations
on the actual code, at the linking step when it becomes possible to
do them with cross-object-file information. These two flags, by
contrast, cause the linker to make certain optimizations within the
scope of its job as the linker.
Documentation is here, though sparse:
https://sourceware.org/binutils/docs-2.31/ld/Options.html
The meaning of -O1 was explained in more detail in this LWN article:
https://lwn.net/Articles/192624/
Apparently it makes the resulting symbol table use a bigger hash
table, so the load factor is smaller and lookups are faster. Cool.
As for -Bsymbolic-functions, the documentation indicates that it's a
way of saving lookups through the symbol table entirely. There can
apparently be situations where it changes the behavior of a program,
specifically if the program relies on linker tricks to provide
customization features:
https://bugs.launchpad.net/ubuntu/+source/xfe/+bug/644645https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=637184#35
But I'm pretty sure CPython doesn't permit that kind of trick: you
don't load a shared object that tries to redefine some symbol found
in the interpreter core.
The stronger reason I'm confident using -Bsymbolic-functions is
safe, though, is empirical. Both Debian and Ubuntu have been
shipping a Python built this way since forever -- it was introduced
for the Python 2.4 and 2.5 in Ubuntu "hardy", and Debian "lenny",
released in 2008 and 2009. In those 12 years they haven't seen a
need to drop this flag; and I've been unable to locate any reports
of trouble related to it, either on the Web in general or on the
Debian bug tracker. (There are reports of a handful of other
programs breaking with it, but not Python/CPython.) So that seems
like about as thorough testing as one could hope for.
---
As for the performance impact: I ran CPython upstream's preferred
benchmark suite, "pyperformance", in the same way as described in
the previous commit. On top of that commit's change, the results
across the 60 benchmarks in the suite are:
The median is 6% faster.
The middle half (aka interquartile range) is from 4% to 8% faster.
Out of 60 benchmarks, 3 come out slower, by 1-4%. At the other end,
5 are at least 10% faster, and one is 17% faster.
So, that's quite a material speedup! I don't know how big the
effect of these flags is for other software; but certainly CPython
tends to do plenty of dynamic linking, as that's how it loads
extension modules, which are ubiquitous in the stdlib as well as
popular third-party libraries. So perhaps that helps explain why
optimizing the dynamic linker has such an impact.
