`toTargetArch` in `pkgs/build-support/rust/lib/default.nix` is used to
set `CARGO_CFG_TARGET_ARCH`. This environment variable is supposed to
be the `<arch>` portion of an LLVM-style platform name:
```
<arch><sub>-<kernel>-<libc><abi>
```
Note that the pointer-width (the "64" in "x86_64" and "mips64") is
part of `<arch>`, but the endianness (the `_be` in `aarch64_be`) is
*not*.
Unfortunately at the moment nixpkgs' parsed `cpuType` has no way to
query for the three subparts (name, pointer-width, and
subarch/endianness), nor any way to ask for just the first two parts.
For now, this commit simply fixes the problem in the two cases that
matter: `mips64el` and `powerpc64le`, which I believe are the only two
platforms supported by both rust and nixpkgs which have a
"subarchitecture".
Tell rust if we want our binaries linked statically or dynamically.
Otherwise the compiler will always produce statically linked binaries for musl
targets, as this is the default.
We are replicating one mechanism behind `-Z build-std`.
There isn't yet crate2nix support for this, but one can (and I do) add
the missing stdlib deps (for this feature to pick up) with overrides.
With Rust 1.61, it is necessary to link to external static/dynamic libaries
when building the rlib that uses them, rather than when linking the final
binary. In fact, it is no longer necessary to specify the libraries to link
when building the final binary, but the library search path flags must still
be included.
The old logic flow had the structure
if ( … ) {
if ( … ) {
…
} else {
…
}
} else {
…
}
which is quite hard to follow in Nix. Instead we ensure that no if
expression is inside a then branch.
This change is zero rebuild, as no logic was changed.
This parameter is being set to `$NIX_BUILD_CORES` by default. This is a
standard practice but there's a suspicion that this can produce broken
builds. For some details see
https://github.com/cargo2nix/cargo2nix/issues/184 . As a
work-around/test, it'd be good if codegen-units can be set to something
constant, such as `1`. This PR allows it.
Note that the default of `$NIX_BUILD_CORES` is preserved so this MR
causes no change in default behaviour and no rebuilds.
These features are internal-only, have special characters that bash
doesn't support in variable names, and aren't normally given
environment variables by cargo as far as I can tell.
Some crates do not have a Cargo.toml at the top-level, but only in
nested directories. Before this change importCargoLock used to fail with:
error: manifest path `/nix/store/some-store-path/Cargo.toml` does not exist
- `toRustTarget` and friends pulled out from rust tools into rust
library. Since they don't depend on any packages they can be more
widely useable.
- `build-rust-package` gets its own directory
- `fetch-cargo-tarball` gets its own directory
