Each invocation of pkgs.extends adds 130MB of allocation to the hydra
evaluator. We are already struggling with the amount of memory nixpkgs
requires.
`pkgs.extend` is a useful escape-hatch, but should be not be used inside
of nixpkgs directly.
Consider example:
$ nix-instantiate ./nixos -A system --arg configuration '
{
boot.isContainer = true;
nixpkgs.overlays = [ (self: super: {
nix = self.pkgsStatic.nix;
}) ];
}'
When resolving package through overlays, we figure out that
nix == self.pkgsStatic.nix
=>
nix == (import <nixpkgs> { inherit overlays; }).nix
=>
nix == (import <nixpkgs> { overlays = [(self: super: { nix = self.pkgsStatic.nix; })];}).nix
and we enter infinite recursion of nixpkgs evaluations.
The proper fix should terminate recursion by assigning self fixpoint
to inner custom package set. But I get infinite recursion somehow, so
I use `super`. It is less correct modulo deep custom overrides, but behaves
correctly for simple cases and doesn't OOM evaluator.
Fixes https://github.com/NixOS/nixpkgs/issues/57984
This is needed to avoid confusing and repeated boilerplate for
`fooForTarget`. The vast majority of use-cases can still use
`buildPackages or `targetPackages`, which are now defined in terms of
these.
Whenever we create scripts that are installed to $out, we must use runtimeShell
in order to get the shell that can be executed on the machine we create the
package for. This is relevant for cross-compiling. The only use case for
stdenv.shell are scripts that are executed as part of the build system.
Usages in checkPhase are borderline however to decrease the likelyhood
of people copying the wrong examples, I decided to use runtimeShell as well.
This enables inspection of the currently used overlays. Useful for
usecases where nixpkgs is imported multiple times.
eg. different channels
self: super:
let
latest = import <nixpkgs-trunk> {
inherit (super) config overlays;
};
in
{
hello-custom-latest = latest.hello-custom;
}
Adds the static overlay that can be used to build Nixpkgs statically.
Can be used like:
nix build pkgsStatic.hello
Not all packages build, as some rely on dynamic linking.
For historical reasons, self was ill-named. This removes its usages
from all-packages.nix and provides a deprecation message for those
who use a patched Nixpkgs.
Some packages seem to depend on the peculiarities of res, as can
be seen by making res into an alias of pkgs (normally "self").
The super variable doesn't have all that is needed.
Therefore the simple fix is not guaranteed to work and as such,
usages of res need to be changed to pkgs or super, case by case.
This is something that I have found useful in tests. In practice
I recommend that people call Nixpkgs once for performance and
simplicity. The inline documentation mentions this too.
2a6e4ae49a and
e51f736076 reverted a bit too much, and I
initially missed this when reviewing. The release notes already still
mention this change, too.
Intuitively, one cares mainly about the host platform: Platforms differ
in meaningful ways but compilation is morally a pure process and
probably doesn't care, or those difference are already abstracted away.
@Dezgeg also empirically confirmed that > 95% of checks are indeed of
the host platform.
Yet these attributes in the old cross infrastructure were defined to be
the build platform, for expediency. And this was never before changed.
(For native builds build and host coincide, so it isn't clear what the
intention was.)
Fixing this doesn't affect native builds, since again they coincide. It
also doesn't affect cross builds of anything in Nixpkgs, as these are no
longer used. It could affect external cross builds, but I deem that
unlikely as anyone thinking about cross would use more explicit
attributes for clarity, all the more so because the rarity of inspecting
the build platform.
I don't know when we can/should remove them, but this at least gets
people to stop using them. The preferred alternatives also date back to
17.09 so writing forward-compatable code without extra conditions is
easy.
Beginning with these as they are the least controversial.
I have renamed the overlay to “otherPackageSets” because I think that
is more descriptive.
pkgsLocal has been removed because there were concerns that it would
be confusing. None of the other names seemed very useful so I think it
is best to avoid it altogether. pkgsCross is still included,
hopefully, that will not have as much confusion.
pkgsMusl is now available for building Musl packages. It will give you
packages bulit with the Musl libc.
Also added more documentation.
/cc @dezgeg @Ericson2314 @dtzWill
You can turn on this config option if you want to find references to
aliases in Nixpkgs. Ideally these can be removed from Nixpkgs and
eventually we can remove the alias altogether.
The stdenvOverrides overlay is used to bring packages forward during
bootstrapping via stdenv.overrides. These packages have already had
the overlays applied to them in the previous boostrapping stage. If
stdenvOverrides is not last in the overlays stack, all remaining
overlays will windup being applied again to these packages.
closes#34086
In practice, this is a strictly stronger condition than target != build
as we never have build = target != host. Really, the attribute should
be removed altogether, but for now we make it work for plain libraries,
which do not care about the target platform. In the few cases where the
compilers use this and actually care about the target platform, I'll
manually change them to use `targetPlatform` instead.
Each bootstrapping stage ought to just depend on the previous stage, but
poorly-written compilers break this elegence. This provides an easy-enough
way to depend on the next stage: targetPackages. PLEASE DO NOT USE IT
UNLESS YOU MUST!
I'm hoping someday in a pleasant future I can revert this commit :)
The long term goal is a big replace:
{ inherit system platform; } => buildPlatform
crossSystem => hostPlatform
stdenv.cross => targetPlatform
And additionally making sure each is defined even when not cross compiling.
This commit refactors the bootstrapping code along that vision, but leaves
the old identifiers with their null semantics in place so packages can be
modernized incrementally.
