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
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 gcc in android does not have this on by default. Doing this will
fix some of the errors in cross-trunk:
https://hydra.nixos.org/build/76354538/nixlog/11
This is related to how separate debug info is handled in Nixpkgs.
It wasn’t exactly clear which NDK you were using previously. This adds
an attribute to system that handles what version of the NDK we should
use when building things.
/cc @Ericson2314
This fixes cross compiling to android that is currently broken. The
asm symlink needs to be set on versions /newer/ than 10e not the other
way around. We also need to use hostInfo’s triple here because ...
/cc @ericson2314@bkchr
Ben Siraphob