Before this commit, cc-wrapper/default.nix was using
`isGccArchSupported` to validate `-mtune=` values. This has two
problems:
- On x86, `-mtune=` can take the same values as `-march`, plus two
additional values `generic` and `intel` which are not valid for
`-march`.
- On ARM, `-mtune=` does not take the same values as `-march=`;
instead it takes the same values as `-mcpu`.
This commit fixes these two problems by adding a new
`isGccTuneSupported` function. For `isx86` this returns `true` for
the two special values and otherwise defers to `isGccArchSupported`.
This commit also adds support for `-mtune=` on Aarch64.
Unfortunately on Aarch64, Clang does not accept as wide a variety of
`-mtune=` values as Gcc does. In particular, Clang does not tune
for big.LITTLE mixed-model chips like the very popular RK3399, which
is targeted using `-march=cortex-a72.cortex-a53` in gcc.
To address this problem, this commit also adds a function
`findBestTuneApproximation` which can be used to map
clang-unsupported tunings like `cortex-a72.cortex-a53` to
less-precise tunings like `cortex-a53`.
The work which led to this commit arose because we now have
packages, like `crosvm`, which use *both* `clang` *and* `gcc`.
Previously I had been using `overrideAttrs` to set
`NIX_CFLAGS_COMPILE` on a package-by-package basis based on which
compiler that package used. Since we now have packages which use
*both* compilers, this strategy no longer works.
I briefly considered splitting `NIX_CFLAGS_COMPILE` into
`NIX_CFLAGS_COMPILE_GCC` and `NIX_CFLAGS_COMPILE_CLANG`, but since
`NIX_CFLAGS_COMPILE` is sort of a hack to begin with I figured that
adding the logic to `cc-wrapper` would be preferable.
* doc/stdenv: rewrite manual build procedure to be closer to an auto-build
This is based on
<https://jade.fyi/blog/building-nix-derivations-manually/> plus some
more original research.
The previous version of this section did not work for your choice of
simple Haskell package, e.g. haskellPackages.hscolour, due to things
like `compileBuildDriverPhase` and other custom phases that it
does not address at all.
It seems more correct to use genericBuild in development to harmonize it
with what is actually done.
I feel a little bit like I am committing a sin by suggesting using the
experimental CLI in the manual (afaict I am the first to do this), but I
have given the old version of the command, and there are justifiable
reasons to do it:
* The noted limitations with env-vars are fixed. The one with the
non-empty temp directory was one I ran into myself and oh boy was that
not fun to debug.
* Additionally the outputs are set *before* sourcing `setup.sh`: there
is an issue with nix-shell where the original version of `$out` winds
up in `NIX_LDFLAGS` due to _addRpathPrefix, which means that resulting
executables may not run properly.
It is sad that `nix develop` propagates a wrong value of `SHELL` to
builders, though. It is equally sad that `nix-shell` is essentially
abandoned upstream, with undocumented and not insignificant differences
from `nix develop`.
For the exact script differences:
17e6b85d05/src/nix-build/nix-build.cc (L516-L551)db026103b1/src/nix/get-env.sh
Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>
systemdMinimal is used to break the dependency cycle of libraries
required by systemd on itself. The problem is that this means that
every system closure will have two sets of systemd binaries in the
closure. This wastes around 10 MiB in every system closure.
Add the option to systemd to only ship libudev and libsystemd instead
of a whole systemd installation.
Projects building with meson are currently installTargets. Map these
to install tags, which are roughly equivalent. This allows projects to
selectively install components.
The idea is to run an async process waiting for swtpm
and we have to ensure that `FD_CLOEXEC` is cleared on this process'
stdin file descriptor, we use `fdflags` for this, a loadable builtin in
Bash ≥ 5.
The async process when exited will terminate `swtpm`, we bind the
termination of the async process to the termination of QEMU by virtue of
having `qemu` exec in that Bash script.
Signed-off-by: Arthur Gautier <baloo@superbaloo.net>
Co-authored-by: Raito Bezarius <masterancpp@gmail.com>
