Following legacy packing conventions, `isArm` was defined just for
32-bit ARM instruction set. This is confusing to non packagers though,
because Aarch64 is an ARM instruction set.
The official ARM overview for ARMv8[1] is surprisingly not confusing,
given the overall state of affairs for ARM naming conventions, and
offers us a solution. It divides the nomenclature into three levels:
```
ISA: ARMv8 {-A, -R, -M}
/ \
Mode: Aarch32 Aarch64
| / \
Encoding: A64 A32 T32
```
At the top is the overall v8 instruction set archicture. Second are the
two modes, defined by bitwidth but differing in other semantics too, and
buttom are the encodings, (hopefully?) isomorphic if they encode the
same mode.
The 32 bit encodings are mostly backwards compatible with previous
non-Thumb and Thumb encodings, and if so we can pun the mode names to
instead mean "sets of compatable or isomorphic encodings", and then
voilà we have nice names for 32-bit and 64-bit arm instruction sets
which do not use the word ARM so as to not confused either laymen or
experienced ARM packages.
[1]: https://developer.arm.com/products/architecture/a-profile
This involved:
* Installing miniperl as $dev/bin/perl
* Setting miniperl to take INC from
lib/perl5/{site_perl/,}cross_perl/${version} as well as
lib/perl5/{site_perl/,}/${version}/${runtimeArch}, in that
order. miniperl taking from runtimeArch is not really correct, but
it works in some pure-perl cases (e.g. Config.pm) and can be
overridden with the cross_perl variant.
* Installing perl-cross's stubs into
$dev/lib/perl5/cross_perl/${version}
* Patching MakeMaker.pm to gracefully degrade (very slightly) if B.pm
can't be loaded, which it can't in cross-compilation.
* Passing the right build-time and runtime perls to Makefile.PL
The following parameters are now available:
* hardeningDisable
To disable specific hardening flags
* hardeningEnable
To enable specific hardening flags
Only the cc-wrapper supports this right now, but these may be reused by
other wrappers, builders or setup hooks.
cc-wrapper supports the following flags:
* fortify
* stackprotector
* pie (disabled by default)
* pic
* strictoverflow
* format
* relro
* bindnow
This is a major closure size reduction on Darwin, and probably a less
significant one on Linux. On darwin, retaining the compiler means adding
clang and its dependency llvm to the perl closure, which gives us ~400MB
of extra stuff. Considering that Nix itself depends on this version of
perl, that makes cutting a new Nix release rather unpleasaont Darwin.
After this patch, I was able to get the `nixUnstable` closure down to
21MB after feeding it into a .tar.xz (123MB before compression). There's
still room for improvement but this should carry us over until we split
outputs.
