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Motivation

We start with rust/cargo on linux to make it work with nix as backend, see https://github.com/NixOS/nix/pull/8699 for this

• https://lastlog.de/blog/libnix_roadmap.html#cargo-with-nix-support
• https://github.com/NixOS/nix/pull/8699
• https://github.com/Anillc/nixrs/pull/1

Working branch

https://github.com/nixcloud/cargo/tree/libnix-0.79.0

both folders ~/.cargo and carto/target have been removed and then a cargo build in ~/cargo will fill these.

~/.cargo

[nixos@nixos:~/cargo]$ du -sh ~/.cargo
239M    /home/nixos/.cargo

[nixos@nixos:~/cargo]$ ls ~/.cargo/
registry

[nixos@nixos:~/cargo]$ ls ~/.cargo/registry/
cache  CACHEDIR.TAG  index  src

~/cargo

the example is the cargo itself, the tool coming with the rust toolchain, since we hack on it.

[nixos@nixos:~/cargo]$ du -sh target/
2.3G    target/

[nixos@nixos:~/cargo]$ ls target/
CACHEDIR.TAG  debug

[nixos@nixos:~/cargo]$ ls target/debug/
build  cargo  cargo.d  deps  examples  incremental  libcargo.d  libcargo.rlib

Plan

libnix backend in cargo needs to get these things working:

• no use of ~/.cargo, everything in /nix/store
• target/debug/* needs to come from /nix/store, eventually symlinked or transparently from the store

figure out what these are:

• target/debug/build

.fingerprint

target/debug/.fingerprint -> https://doc.rust-lang.org/nightly/nightly-rustc/cargo/core/compiler/fingerprint/index.html

[nixos@nixos:~/cargo]$ ls target/debug/.fingerprint/der-d0714c795318982b/
dep-lib-der  invoked.timestamp  lib-der  lib-der.json

[nixos@nixos:~/cargo]$ cat target/debug/.fingerprint/der-d0714c795318982b/lib-der
6b2cf10d51d11828

[nixos@nixos:~/cargo]$ cat target/debug/.fingerprint/der-d0714c795318982b/lib-der.json
{"rustc":18217185010275080438,"features":"[\"alloc\", \"oid\", \"pem\", \"std\", \"zeroize\"]","declared_features":"","target":4346314333490370059,"profile":12206360443249279867,"path":16879011525611689376,"deps":[[1724196337906130016,"pem_rfc7468",false,5466269655917579261],[2676387858222833023,"const_oid",false,2852573652909154018],[15098350142499636151,"zeroize",false,14469829910961900562]],"local":[{"CheckDepInfo":{"dep_info":"debug/.fingerprint/der-d0714c795318982b/dep-lib-der"}}],"rustflags":[],"metadata":12456048820742377390,"config":2202906307356721367,"compile_kind":0}

[nixos@nixos:~/cargo]$ cat target/debug/.fingerprint/der-d0714c795318982b/dep-lib-der

finally:

• get a crate compiled without dependencies
• get one with nested dependencies
• get one with c library usage (like cargo itself)