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John Ericson bf17d6dacf top-level: Introduce buildPackages for resolving build-time deps
[N.B., this package also applies to the commits that follow it in the same
PR.]

In most cases, buildPackages = pkgs so things work just as before. For
cross compiling, however, buildPackages is resolved as the previous
bootstrapping stage. This allows us to avoid the mkDerivation hacks cross
compiling currently uses today.

To avoid a massive refactor, callPackage will splice together both package
sets. Again to avoid churn, it uses the old `nativeDrv` vs `crossDrv` to do
so. So now, whether cross compiling or not, packages with get a `nativeDrv`
and `crossDrv`---in the non-cross-compiling case they are simply the same
derivation. This is good because it reduces the divergence between the
cross and non-cross dataflow. See `pkgs/top-level/splice.nix` for a comment
along the lines of the preceding paragraph, and the code that does this
splicing.

Also, `forceNativeDrv` is replaced with `forceNativePackages`. The latter
resolves `pkgs` unless the host platform is different from the build
platform, in which case it resolves to `buildPackages`. Note that the
target platform is not important here---it will not prevent
`forcedNativePackages` from resolving to `pkgs`.

--------

Temporarily, we make preserve some dubious decisions in the name of preserving
hashes:

Most importantly, we don't distinguish between "host" and "target" in the
autoconf sense. This leads to the proliferation of *Cross derivations
currently used. What we ought to is resolve native deps of the cross "build
packages" (build = host != target) package set against the "vanilla
packages" (build = host = target) package set. Instead, "build packages"
uses itself, with (informally) target != build in all cases.

This is wrong because it violates the "sliding window" principle of
bootstrapping stages that shifting the platform triple of one stage to the
left coincides with the next stage's platform triple. Only because we don't
explicitly distinguish between "host" and "target" does it appear that the
"sliding window" principle is preserved--indeed it is over the reductionary
"platform double" of just "build" and "host/target".

Additionally, we build libc, libgcc, etc in the same stage as the compilers
themselves, which is wrong because they are used at runtime, not build
time. Fixing this is somewhat subtle, and the solution and problem will be
better explained in the commit that does fix it.

Commits after this will solve both these issues, at the expense of breaking
cross hashes. Native hashes won't be broken, thankfully.

--------

Did the temporary ugliness pan out? Of the packages that currently build in
`release-cross.nix`, the only ones that have their hash changed are
`*.gcc.crossDrv` and `bootstrapTools.*.coreutilsMinimal`. In both cases I
think it doesn't matter.

 1. GCC when doing a `build = host = target = foreign` build (maximally
    cross), still defines environment variables like `CPATH`[1] with
    packages.  This seems assuredly wrong because whether gcc dynamically
    links those, or the programs built by gcc dynamically link those---I
    have no idea which case is reality---they should be foreign. Therefore,
    in all likelihood, I just made the gcc less broken.

 2. Coreutils (ab)used the old cross-compiling infrastructure to depend on
    a native version of itself. When coreutils was overwritten to be built
    with fewer features, the native version it used would also be
    overwritten because the binding was tight. Now it uses the much looser
    `BuildPackages.coreutils` which is just fine as a richer build dep
    doesn't cause any problems and avoids a rebuild.

So, in conclusion I'd say the conservatism payed off. Onward to actually
raking the muck in the next PR!

[1]: https://gcc.gnu.org/onlinedocs/gcc/Environment-Variables.html
2017-01-24 11:37:56 -05:00

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Nix

/* This file composes a single bootstrapping stage of the Nix Packages
collection. That is, it imports the functions that build the various
packages, and calls them with appropriate arguments. The result is a set of
all the packages in the Nix Packages collection for some particular platform
for some particular stage.
Default arguments are only provided for bootstrapping
arguments. Normal users should not import this directly but instead
import `pkgs/default.nix` or `default.nix`. */
{ # The system (e.g., `i686-linux') for which to build the packages.
system
, # the package set used at build-time
buildPackages
, # The standard environment to use for building packages.
stdenv
, # This is used because stdenv replacement and the stdenvCross do benefit from
# the overridden configuration provided by the user, as opposed to the normal
# bootstrapping stdenvs.
allowCustomOverrides
, # Non-GNU/Linux OSes are currently "impure" platforms, with their libc
# outside of the store. Thus, GCC, GFortran, & co. must always look for
# files in standard system directories (/usr/include, etc.)
noSysDirs ? (system != "x86_64-freebsd" && system != "i686-freebsd"
&& system != "x86_64-solaris"
&& system != "x86_64-kfreebsd-gnu")
, # The configuration attribute set
config
, overlays # List of overlays to use in the fix-point.
, crossSystem
, platform
, lib
, nixpkgsFun
}:
let
stdenvAdapters = self: super:
let res = import ../stdenv/adapters.nix self; in res // {
stdenvAdapters = res;
};
trivialBuilders = self: super:
import ../build-support/trivial-builders.nix {
inherit lib; inherit (self) stdenv stdenvNoCC; inherit (self.xorg) lndir;
};
stdenvBootstappingAndPlatforms = self: super: {
stdenv = stdenv // { inherit platform; };
buildPackages = buildPackages // { recurseForDerivations = false; };
inherit
system platform crossSystem;
};
splice = self: super: import ./splice.nix lib self;
allPackages = self: super:
let res = import ./all-packages.nix
{ inherit lib nixpkgsFun noSysDirs config; }
res self;
in res;
aliases = self: super: import ./aliases.nix super;
# stdenvOverrides is used to avoid having multiple of versions
# of certain dependencies that were used in bootstrapping the
# standard environment.
stdenvOverrides = self: super:
(super.stdenv.overrides or (_: _: {})) self super;
# Allow packages to be overridden globally via the `packageOverrides'
# configuration option, which must be a function that takes `pkgs'
# as an argument and returns a set of new or overridden packages.
# The `packageOverrides' function is called with the *original*
# (un-overridden) set of packages, allowing packageOverrides
# attributes to refer to the original attributes (e.g. "foo =
# ... pkgs.foo ...").
configOverrides = self: super:
lib.optionalAttrs allowCustomOverrides
((config.packageOverrides or (super: {})) super);
# The complete chain of package set builders, applied from top to bottom
toFix = lib.foldl' (lib.flip lib.extends) (self: {}) ([
stdenvBootstappingAndPlatforms
stdenvAdapters
trivialBuilders
splice
allPackages
aliases
stdenvOverrides
configOverrides
] ++ overlays);
in
# Return the complete set of packages.
lib.fix toFix