Compilers in nixpkgs have caught up and major distros
should also have recent enough compilers. It would be
nice to have newer features like more full featured
ranges and deducing this.
The implicit dependency on refLength (which is the StorePath::HashLen)
is not good. Also the companion tests and benchmarks are already in libstore-tests.
Make it separate from Hash, since other things can be base-encoded too.
This isn't really needed for Nix, but it makes the code easier to read
e.g. for someone reimplementing this stuff in a different language. (Of
course, Base16/Base64 should be gotten off-the-shelf, but now the hash
code, which is more bespoke, is less cluttered with the parts that would
be from some library.)
Many reimplementations of "Nix32" and our hash type already exist, so
this cleanup is coming years too late, but I say better late than never
/ it is always good to nudge the code in the direction of being a
"living spec".
Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
Unlike std::sort and std::stable_sort, this implementation
does not lead to out-of-bounds memory reads or other undefined
behavior when the predicate is not strict weak ordering.
This makes it possible to use this function in libexpr for
builtins.sort, where an incorrectly implemented comparator
in the user nix code currently can crash and burn the evaluator
by invoking C++ UB.
There are two big changes:
1. Public and private config is now separated. Configuration variables
that are only used internally do not go in a header which is
installed.
(Additionally, libutil has a unix-specific private config header,
which should only be used in unix-specific code. This keeps things a
bit more organized, in a purely private implementation-internal way.)
2. Secondly, there is no more `-include`. There are very few config
items that need to be publically exposed, so now it is feasible to
just make the headers that need them just including the (public)
configuration header.
And there are also a few more small cleanups on top of those:
- The configuration files have better names.
- The few CPP variables that remain exposed in the public headers are
now also renamed to always start with `NIX_`. This ensures they should
not conflict with variables defined elsewhere.
- We now always use `#if` and not `#ifdef`/`#ifndef` for our
configuration variables, which helps avoid bugs by requiring that
variables must be defined in all cases.
- Some headers were completely redundant and have been removed.
- Other headers have been turned private.
- Unnecessary meson.build code has been removed.
- libutil-tests now has a private config header, where previously
it had none. This removes the need to expose a package version
macro publicly.
Fix a footgun. In my case, I had a couple of build ("output")
directories sitting around.
rm -rf build-*
Was confused for a bit why a meson.build file was missing.
Probably also helps with autocompletion.
I tried meson-build-support first, but I had to add something like
a nix- prefix, in order to make meson happy. They've reserved the
meson- prefix.
This reduces the amount of boilerplate. More importantly, it provides
a place to add compiler flags (such as -O3) without having to add it
to every subproject (and the risk of forgetting to include it).
