Since Rust 1.83.0, `rust-src` component leads to bloated runtime dependencies

[veehaitch]

The commit that introduces Rust 1.83.0 (b259ef7) appears to bloat the closure of packages built with the rust toolchain that have the rust-src component.

rust-toolchain.toml:

[toolchain]
channel = "stable"
components = [ "rust-src" ]
targets = [ "x86_64-unknown-linux-gnu" ]

default.nix (adapted the example from the nixpkgs manual):

with import <nixpkgs>
{
  overlays = [
    (import (fetchTarball "https://github.com/oxalica/rust-overlay/archive/34971069ec33755b2adf2481851f66d8ec9a6bfa.tar.gz"))
  ];
};
let
  rustToolchain = rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
  rustPlatform = makeRustPlatform {
    cargo = rustToolchain;
    rustc = rustToolchain;
  };
in

rustPlatform.buildRustPackage rec {
  pname = "ripgrep";
  version = "12.1.1";

  src = fetchFromGitHub {
    owner = "BurntSushi";
    repo = "ripgrep";
    rev = version;
    hash = "sha256-+s5RBC3XSgb8omTbUNLywZnP6jSxZBKSS1BmXOjRF8M=";
  };

  cargoHash = "sha256-l1vL2ZdtDRxSGvP0X/l3nMw8+6WF67KPutJEzUROjg8=";

  doCheck = false;

  meta = {
    description = "Fast line-oriented regex search tool, similar to ag and ack";
    homepage = "https://github.com/BurntSushi/ripgrep";
    license = with lib.licenses; [ mit unlicense ];
    maintainers = with lib.maintainers; [];
  };
}

# nix-build
# nix path-info --recursive --size --closure-size --human-readable ./result
/nix/store/4hcdxyjf9yiq7qf3i4548drb6sjmwa1v-xgcc-13.3.0-libgcc                                   155.9 KiB       155.9 KiB
/nix/store/w19cxz37j5nrkg8w80y91bga89310jgi-libunistring-1.2                                       1.8 MiB         1.8 MiB
/nix/store/jwsdpq2yxw43ixalh93z726czz7bay2j-libidn2-2.3.7                                        352.6 KiB         2.1 MiB
/nix/store/sl141d1g77wvhr050ah87lcyz2czdxa3-glibc-2.40-36                                         28.8 MiB        31.1 MiB
/nix/store/5frxzv8fj2zaj04lbv3z848p8zvwpz3g-gmp-6.3.0                                            706.6 KiB        31.8 MiB
/nix/store/bklfkdh58y2hr24796hln00l2ly68fvg-mpfr-4.2.1                                           775.7 KiB        32.5 MiB
/nix/store/d72018202lbgj7ckmd020d56apny73wg-libmpc-1.3.1                                         277.4 KiB        32.8 MiB
/nix/store/haci0d018njygwdga95bsbx8ww2iswy7-zlib-1.3.1                                           125.2 KiB        31.2 MiB
/nix/store/kskaix9pdvh22pkgnaqd3k9yd7r1xh1z-isl-0.20                                               2.5 MiB        34.3 MiB
/nix/store/1qx77645wk0rd00h49rvjh9vkgs8vwvy-linux-headers-6.10                                     6.5 MiB         6.5 MiB
/nix/store/vpsla1ivhavzd4fmi95yzmgb4g9rd072-glibc-2.40-36-bin                                      2.7 MiB        33.7 MiB
/nix/store/n15bxkd7id2gvlwpihm4kp675aqkrwmj-glibc-2.40-36-dev                                      2.3 MiB        42.6 MiB
/nix/store/lw294qfdnf29lhxqwzy9byrmx975rvn9-gcc-13.3.0-libgcc                                    155.9 KiB       155.9 KiB
/nix/store/y3kdn61k93rq2jx1lj2x72lnsk0l92qh-gcc-13.3.0-lib                                         8.7 MiB        39.9 MiB
/nix/store/0vsyw5bhwmisszyfd1a0sdnwvnf4qa5a-gcc-13.3.0                                           220.7 MiB       276.5 MiB
/nix/store/56nav6x43mv8b5bipazq4d9ycr1ngvav-expand-response-params                                16.4 KiB        31.1 MiB
/nix/store/717iy55ncqs0wmhdkwc5fg2vci5wbmq8-bash-5.2p32                                            1.6 MiB        32.6 MiB
/nix/store/j6z0q427f6jm3d9mmrb4pgz72i93yp2f-attr-2.5.2                                            90.6 KiB        31.2 MiB
/nix/store/4ac0simsl36mz7ksv64ag7nmpc86s1mh-acl-2.3.2                                            125.2 KiB        31.3 MiB
/nix/store/w3jiv6xd520k1d1rvhxn7mr0pqzindjs-gmp-with-cxx-6.3.0                                   749.0 KiB        40.6 MiB
/nix/store/ph44jcx3ddmlwh394mh1wb7f1qigxqb1-coreutils-9.5                                          1.4 MiB        42.3 MiB
/nix/store/88rlbc5ka2m5zir98ajkgpqkb1i82wcs-rustc-1.83.0-x86_64-unknown-linux-gnu                318.5 MiB       362.5 MiB
/nix/store/0w0sbmymx7xify583f78djpx0c47xhqv-rustfmt-preview-1.83.0-x86_64-unknown-linux-gnu       10.9 MiB       373.5 MiB
/nix/store/zxk207030dbrz6ikiq61sz2c08gpljxq-pcre2-10.44                                            1.8 MiB        32.9 MiB
/nix/store/20s3724qq3g0j14v6zc0s7z16k7i3j39-libselinux-3.7                                         1.2 MiB        34.1 MiB
/nix/store/hc7rrrmb1wilsldsii4fbmvcl68lijsl-util-linux-minimal-2.39.4-lib                          1.8 MiB        32.9 MiB
/nix/store/pmf31rbzvv618qirwmzppjb63wsrl4zi-libffi-3.4.6                                          71.9 KiB        31.2 MiB
/nix/store/fxnchbq09sq279ssqdsgzigsyvp6hz06-glib-2.80.4                                           14.7 MiB        50.8 MiB
/nix/store/ncznv9xrbi34k4zlnd25dp7kyaqjscn7-libgpg-error-1.50                                    832.7 KiB        31.9 MiB
/nix/store/mxqw137xwdd4fgnna0z4a7j8cx969br8-libgcrypt-1.10.3-lib                                   1.4 MiB        33.3 MiB
/nix/store/spvci786gald6nsf7z5a095fsc1dc3xx-libsecret-0.21.4                                     672.8 KiB        53.6 MiB
/nix/store/9x0gj79aslszsgn8qcgwxv6ni27szl00-cargo-1.83.0-x86_64-unknown-linux-gnu                 33.4 MiB        87.2 MiB
/nix/store/c1n8g5129aycgj4cxxgry8460ki7glfj-binutils-2.43.1-lib                                    2.8 MiB        34.0 MiB
/nix/store/jp66i2lg1p2s8lkwsqh33c3913rgdq8j-clippy-preview-1.83.0-x86_64-unknown-linux-gnu        13.8 MiB       376.3 MiB
/nix/store/nzmp6x4694fn4al0dxq4g1q4fr4yyg7l-rust-std-1.83.0-x86_64-unknown-linux-gnu             146.9 MiB       147.1 MiB
/nix/store/v9znmjrv9f18072n1y1g5caf9irzs6v2-rust-docs-1.83.0-x86_64-unknown-linux-gnu            659.1 MiB       659.1 MiB
/nix/store/vcvhwiilizhijk7ywyn58p9l005n9sbn-binutils-2.43.1                                       30.1 MiB        72.9 MiB
/nix/store/l7n97992gd5piaw8phkxzsz176gfk1yj-binutils-wrapper-2.43.1                               50.0 KiB        88.3 MiB
/nix/store/lvnwdmnjm7nvaq0a3vhvvn46iy4ql7gr-gnugrep-3.11                                         926.6 KiB        33.8 MiB
/nix/store/vh9fsdhgxcnab2qk7vdp2palkkn6j3cp-gcc-wrapper-13.3.0                                    61.8 KiB       316.1 MiB
/nix/store/vpg1chc5fncwvd5fh6j9nywx0bcdpf04-rust-src-1.83.0-x86_64-unknown-linux-gnu              32.1 MiB        64.8 MiB
/nix/store/frx5kr6cmy43qij0kcif59z47pdhkik3-rust-default-1.83.0                                  180.5 MiB         1.7 GiB
/nix/store/hchmc1f3czwxxn1q8nk9ya9h50cnyn1p-ripgrep-12.1.1                                         4.9 MiB         1.7 GiB

When using b259ef7:

# nix-build
# nix path-info --recursive --size --closure-size --human-readable ./result
/nix/store/4hcdxyjf9yiq7qf3i4548drb6sjmwa1v-xgcc-13.3.0-libgcc   155.9 KiB       155.9 KiB
/nix/store/w19cxz37j5nrkg8w80y91bga89310jgi-libunistring-1.2       1.8 MiB         1.8 MiB
/nix/store/jwsdpq2yxw43ixalh93z726czz7bay2j-libidn2-2.3.7        352.6 KiB         2.1 MiB
/nix/store/sl141d1g77wvhr050ah87lcyz2czdxa3-glibc-2.40-36         28.8 MiB        31.1 MiB
/nix/store/lw294qfdnf29lhxqwzy9byrmx975rvn9-gcc-13.3.0-libgcc    155.9 KiB       155.9 KiB
/nix/store/y3kdn61k93rq2jx1lj2x72lnsk0l92qh-gcc-13.3.0-lib         8.7 MiB        39.9 MiB
/nix/store/41zm31n8rnd9wb207fpz430dwydhqg3s-ripgrep-12.1.1         4.9 MiB        44.8 MiB

[oxalica]

Cause: rust-lang/rust#129687
Since 1.83, rustc will discover and embed local std path in the binary if possible, which results in a runtime dependency. Before that, a virtual path /rust/<hash> is used.

You can workaround it for now via --remap-path-prefix like this. I'm not sure if this can be solely fixed in rust-overlay. We may need to add the remap flag in rustPlatform.buildRustPackage's implementation. The embedded path seems to be$(rustc --print sysroot)/lib/rustlib/src/rust/library.

[oxalica]

According to the upstream comment: rust-lang/rust#129687 (comment)

There are 2 solutions:

1. Use a minimal toolchain for build system, thus eliminating rust-src component from build closure at all. I'd 👍 on this, because dev toolchains and release toolchains are expected to be different. You also want to shrink build dependencies from these extensions.
   Nixpkgs' rust toolchain is also minimized and does not carry rust-src by default, so it is free from this issue.
2. If you want to use a full-blown dev toolchains with rust-src for the build anyway, add a remap flag in preConfigure:

   rustSrcBase="$(rustc --print=sysroot)/lib/rustlib/src/rust"
   export RUSTFLAGS="--remap-path-prefix=$rustSrcBase=/"

I don't think it's actionable in rust-overlay part. So I'm closing for now.

[veehaitch]

Thank you for addressing this so quickly! 🙏🏼

[gabyx]

Here is a stupid script to anaylyze the binary:
https://gist.github.com/gabyx/6df210f3f67ea24ca826697a0c6cb845

Usage:

anaylze-binary.sh "$(nix build -L "<installable>" --print-out-paths)/bin/<your-exe-name>" --with-strings

as complementary analysis with nix-tree etc