It is useful to make these dynamic and not bake them into gcc. This
means we don’t have to rebuild gcc to change these values. Instead, we
will pass cflags to gcc based on platform values. This was already
done hackily for android gcc (which is multi-target), but not for our
own gccs which are single target.
To accomplish this, we need to add a few things:
- add ‘arch’ to cpu
- add NIX_CFLAGS_COMPILE_BEFORE flag (goes before args)
- set -march everywhere
- set mcpu, mfpu, mmode, and mtune based on targetPlatform.gcc flags
cc-wrapper: only set -march when it is in the cpu type
Some architectures don’t have a good mapping of -march. For instance
POWER architecture doesn’t support the -march flag at all!
https://gcc.gnu.org/onlinedocs/gcc/RS_002f6000-and-PowerPC-Options.html#RS_002f6000-and-PowerPC-Options
This makes us less reliant on the systems/examples.nix. You should be
able to cross compile with just your triple:
$ nix build --arg crossSystem '{ config = "armv6l-unknown-linux-gnueabi"; }' stdenv
ppc64le and ppc64 are different targets in the configure script. We
can’t use the same one.
TODO: canonicalize similar ones based on qemu’s configure script.
New android ndk (18) now uses clang. We were going through the wrapper
that are provided. This lead to surprising errors when building.
Ideally we could use the llvm linker as well, but this leads to errors
as many packages don’t support the llvm linker.
The explicit remove helped to uncover some hidden uses of `optionSet`
in NixOps. However it makes life harder for end-users of NixOps - it will
be impossible to deploy 19.03 systems with old NixOps, but there is no
new release of NixOps with `optionSet` fixes.
Also, "deprecation" process isn't well defined. Even that `optionSet` was
declared "deprecated" for many years, it was never announced. Hence, I
leave "deprecation" announce. Then, 3 releases after announce,
we can announce removal of this feature.
This type has to be removed, not `throw`-ed in runtime, because it makes
some perfectly fine code to fail. For example:
```
$ nix-instantiate --eval -E '(import <nixpkgs/lib>).types' --strict
trace: `types.list` is deprecated; use `types.listOf` instead
error: types.optionSet is deprecated; use types.submodule instead
(use '--show-trace' to show detailed location information)
```
Comments on conflicts:
- llvm: d6f401e1 vs. 469ecc70 - docs for 6 and 7 say the default is
to build all targets, so we should be fine
- some pypi hashes: they were equivalent, just base16 vs. base32
