nix: build with Mold linker on x86_64-linux

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I771c36297577aba189058a2183ec2b4a6a6a6964

.cargo/config.toml

@@ -0,0 +1,4 @@
+# https://github.com/rui314/mold?tab=readme-ov-file#how-to-use
+[target.'cfg(target_os = "linux")']
+linker = "clang"
+rustflags = ["-C", "link-arg=-fuse-ld=mold"]

.github/dependabot.yml

@@ -0,0 +1,14 @@
+version: 2
+updates:
+  # Update Cargo deps
+  - package-ecosystem: cargo
+    directory: "/"
+    schedule:
+      interval: "weekly"
+
+  # Update used workflows
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: daily
+

.github/workflows/hotpath-comment.yml

@@ -1,12 +1,13 @@
-name: Hotpath Comment
+name: hotpath-comment
 
 on:
   workflow_run:
-    workflows: ["Hotpath Profile"]
+    workflows: ["hotpath-profile"]
     types:
       - completed
 
 permissions:
+  contents: read
   pull-requests: write
 
 jobs:
@@ -15,17 +16,17 @@ jobs:
     if: ${{ github.event.workflow_run.conclusion == 'success' }}
 
     steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
       - name: Download profiling results
-        uses: actions/download-artifact@v4
+        uses: actions/download-artifact@v6
         with:
           name: hotpath-results
+          path: /tmp/
           github-token: ${{ secrets.GITHUB_TOKEN }}
           run-id: ${{ github.event.workflow_run.id }}
 
-      - name: Read PR number
-        id: pr
-        run: echo "number=$(cat pr_number.txt)" >> $GITHUB_OUTPUT
-
       - name: Setup Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
 
@@ -33,17 +34,29 @@ jobs:
         run: cargo install hotpath
 
       - name: Post timing comparison comment
+        env:
+          GH_TOKEN: ${{ github.token }}
         run: |
+          set -euo pipefail
+          HEAD_METRICS=$(cat /tmp/head_timing.json)
+          BASE_METRICS=$(cat /tmp/base_timing.json)
+          PR_NUMBER=$(cat /tmp/pr_number.txt)
           hotpath profile-pr \
-             --head-metrics head-timing.json \
-             --base-metrics base-timing.json \
-             --github-token ${{ secrets.GITHUB_TOKEN }} \
-             --pr-number ${{ steps.pr.outputs.number }}
+            --head-metrics "$HEAD_METRICS" \
+            --base-metrics "$BASE_METRICS" \
+            --github-token "$GH_TOKEN" \
+            --pr-number "$PR_NUMBER"
 
       - name: Post allocation comparison comment
+        env:
+          GH_TOKEN: ${{ github.token }}
         run: |
+          set -euo pipefail
+          HEAD_METRICS=$(cat /tmp/head_alloc.json)
+          BASE_METRICS=$(cat /tmp/base_alloc.json)
+          PR_NUMBER=$(cat /tmp/pr_number.txt)
           hotpath profile-pr \
-             --head-metrics head-alloc.json \
-             --base-metrics base-alloc.json \
-             --github-token ${{ secrets.GITHUB_TOKEN }} \
-             --pr-number ${{ steps.pr.outputs.number }}
+            --head-metrics "$HEAD_METRICS" \
+            --base-metrics "$BASE_METRICS" \
+            --github-token "$GH_TOKEN" \
+            --pr-number "$PR_NUMBER"

.github/workflows/hotpath-profile.yml

@@ -1,4 +1,4 @@
-name: Hotpath Profile
+name: hotpath-profile
 
 on:
   pull_request:
@@ -13,7 +13,9 @@ jobs:
     
     steps:
       - name: Checkout PR HEAD
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
       
       - name: Setup Rust
         uses: actions-rust-lang/setup-rust-toolchain@v1
@@ -22,42 +24,42 @@ jobs:
         env:
           HOTPATH_JSON: "true"
         run: |
-          cargo run --features='hotpath' 2>&1 | grep '^{"hotpath_profiling_mode"' > head-timing.json
+          cargo run --features='hotpath' 2>&1 | grep '^{"hotpath_profiling_mode"' > /tmp/head_timing.json
       
       - name: Run allocation profiling on HEAD
         env:
           HOTPATH_JSON: "true"
         run: |
-          cargo run --features='hotpath,hotpath-alloc-count-total' 2>&1 | grep '^{"hotpath_profiling_mode"' > head-alloc.json
+          cargo run --features='hotpath,hotpath-alloc' 2>&1 | grep '^{"hotpath_profiling_mode"' > /tmp/head_alloc.json
       
       - name: Checkout base branch
-        uses: actions/checkout@v4
-        with:
-          ref: ${{ github.event.pull_request.base.sha }}
+        run: |
+          git checkout ${{ github.event.pull_request.base.sha }}
       
       - name: Run timing profiling on base
         env:
           HOTPATH_JSON: "true"
         run: |
-          cargo run --features='hotpath' 2>&1 | grep '^{"hotpath_profiling_mode"' > base-timing.json
+          cargo run --features='hotpath' 2>&1 | grep '^{"hotpath_profiling_mode"' > /tmp/base_timing.json || echo '{}' > /tmp/base_timing.json
       
       - name: Run allocation profiling on base
         env:
           HOTPATH_JSON: "true"
         run: |
-          cargo run --features='hotpath,hotpath-alloc-count-total' 2>&1 | grep '^{"hotpath_profiling_mode"' > base-alloc.json
+          cargo run --features='hotpath,hotpath-alloc' 2>&1 | grep '^{"hotpath_profiling_mode"' > /tmp/base_alloc.json || echo '{}' > /tmp/base_alloc.json
       
       - name: Save PR number
-        run: echo "${{ github.event.number }}" > pr_number.txt
+        run: |
+          echo '${{ github.event.pull_request.number }}' > /tmp/pr_number.txt
       
       - name: Upload profiling results
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@v5
         with:
           name: hotpath-results
           path: |
-            head-timing.json
-            head-alloc.json
-            base-timing.json
-            base-alloc.json
-            pr_number.txt
+            /tmp/head_timing.json
+            /tmp/head_alloc.json
+            /tmp/base_timing.json
+            /tmp/base_alloc.json
+            /tmp/pr_number.txt
           retention-days: 1

.github/workflows/rust.yml

@@ -10,12 +10,45 @@ env:
   CARGO_TERM_COLOR: always
 
 jobs:
-  build:
-
-    runs-on: ubuntu-latest
+  test:
+    name: Test on ${{ matrix.target }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            target: x86_64-unknown-linux-gnu
+          - os: ubuntu-latest
+            target: aarch64-unknown-linux-gnu
 
     steps:
     - name: "Checkout"
-      uses: actions/checkout@v4
-    - name: "Build with Cargo"
-      run: cargo build --verbose
+      uses: actions/checkout@v6
+
+    - name: "Setup Rust toolchain"
+      uses: actions-rust-lang/setup-rust-toolchain@v1
+      with:
+        target: ${{ matrix.target }}
+
+    - name: "Install cross-compilation tools"
+      if: matrix.target == 'aarch64-unknown-linux-gnu'
+      run: |
+        sudo apt-get update
+        sudo apt-get install -y gcc-aarch64-linux-gnu
+
+    - name: "Configure linker for aarch64"
+      if: matrix.target == 'aarch64-unknown-linux-gnu'
+      run: |
+        mkdir -p .cargo
+        cat >> .cargo/config.toml << EOF
+        [target.aarch64-unknown-linux-gnu]
+        linker = "aarch64-linux-gnu-gcc"
+        EOF
+
+    - name: "Build"
+      run: cargo build --verbose --target ${{ matrix.target }}
+
+    - name: "Run tests"
+      if: matrix.target == 'x86_64-unknown-linux-gnu'
+      run: cargo test --verbose --target ${{ matrix.target }}

Cargo.lock

@@ -17,6 +17,15 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "alloca"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5a7d05ea6aea7e9e64d25b9156ba2fee3fdd659e34e41063cd2fc7cd020d7f4"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "anes"
 version = "0.1.6"
@@ -271,10 +280,11 @@ dependencies = [
 
 [[package]]
 name = "criterion"
-version = "0.7.0"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e1c047a62b0cc3e145fa84415a3191f628e980b194c2755aa12300a4e6cbd928"
+checksum = "a0dfe5e9e71bdcf4e4954f7d14da74d1cdb92a3a07686452d1509652684b1aab"
 dependencies = [
+ "alloca",
  "anes",
  "cast",
  "ciborium",
@@ -283,6 +293,7 @@ dependencies = [
  "itertools",
  "num-traits",
  "oorandom",
+ "page_size",
  "plotters",
  "rayon",
  "regex",
@@ -294,9 +305,9 @@ dependencies = [
 
 [[package]]
 name = "criterion-plot"
-version = "0.6.0"
+version = "0.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9b1bcc0dc7dfae599d84ad0b1a55f80cde8af3725da8313b528da95ef783e338"
+checksum = "5de36c2bee19fba779808f92bf5d9b0fa5a40095c277aba10c458a12b35d21d6"
 dependencies = [
  "cast",
  "itertools",
@@ -451,6 +462,50 @@ dependencies = [
  "percent-encoding",
 ]
 
+[[package]]
+name = "futures-core"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05f29059c0c2090612e8d742178b0580d2dc940c837851ad723096f87af6663e"
+
+[[package]]
+name = "futures-macro"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "162ee34ebcb7c64a8abebc059ce0fee27c2262618d7b60ed8faf72fef13c3650"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "futures-sink"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e575fab7d1e0dcb8d0c7bcf9a63ee213816ab51902e6d244a95819acacf1d4f7"
+
+[[package]]
+name = "futures-task"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f90f7dce0722e95104fcb095585910c0977252f286e354b5e3bd38902cd99988"
+
+[[package]]
+name = "futures-util"
+version = "0.3.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9fa08315bb612088cc391249efdc3bc77536f16c91f6cf495e6fbe85b20a4a81"
+dependencies = [
+ "futures-core",
+ "futures-macro",
+ "futures-sink",
+ "futures-task",
+ "pin-project-lite",
+ "pin-utils",
+ "slab",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.16"
@@ -502,9 +557,9 @@ checksum = "fc0fef456e4baa96da950455cd02c081ca953b141298e41db3fc7e36b1da849c"
 
 [[package]]
 name = "hotpath"
-version = "0.6.0"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ef44238d7007bbd3c41ce7dbf3d7a4fb224bbf70d6cf3162479138dda0cd6a9e"
+checksum = "08382b985a19a79d95d35e2e201b02cc4b99efe2f47d82f3fd4301bb0005bb68"
 dependencies = [
  "arc-swap",
  "base64",
@@ -513,10 +568,15 @@ dependencies = [
  "colored",
  "crossbeam-channel",
  "eyre",
+ "futures-util",
  "hdrhistogram",
  "hotpath-macros",
+ "libc",
+ "mach2",
+ "pin-project-lite",
  "prettytable-rs",
  "quanta",
+ "regex",
  "serde",
  "serde_json",
  "tiny_http",
@@ -526,9 +586,9 @@ dependencies = [
 
 [[package]]
 name = "hotpath-macros"
-version = "0.6.0"
+version = "0.7.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e7e3443c6f4e5cc69e6b701f7bfca8a5502f0080e94629413346e7b4518d730"
+checksum = "7d618063f89423ebe079a69f5435a13d4909219d4e359757118b75fd05ae65d0"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -758,6 +818,12 @@ version = "0.4.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "13dc2df351e3202783a1fe0d44375f7295ffb4049267b0f3018346dc122a1d94"
 
+[[package]]
+name = "mach2"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dae608c151f68243f2b000364e1f7b186d9c29845f7d2d85bd31b9ad77ad552b"
+
 [[package]]
 name = "memchr"
 version = "2.7.4"
@@ -766,7 +832,7 @@ checksum = "78ca9ab1a0babb1e7d5695e3530886289c18cf2f87ec19a575a0abdce112e3a3"
 
 [[package]]
 name = "microfetch"
-version = "0.4.11"
+version = "0.4.12"
 dependencies = [
  "criterion",
  "hotpath",
@@ -816,6 +882,16 @@ version = "11.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d6790f58c7ff633d8771f42965289203411a5e5c68388703c06e14f24770b41e"
 
+[[package]]
+name = "page_size"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30d5b2194ed13191c1999ae0704b7839fb18384fa22e49b57eeaa97d79ce40da"
+dependencies = [
+ "libc",
+ "winapi",
+]
+
 [[package]]
 name = "percent-encoding"
 version = "2.3.2"
@@ -828,6 +904,12 @@ version = "0.2.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3b3cff922bd51709b605d9ead9aa71031d81447142d828eb4a6eba76fe619f9b"
 
+[[package]]
+name = "pin-utils"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b870d8c151b6f2fb93e84a13146138f05d02ed11c7e7c54f8826aaaf7c9f184"
+
 [[package]]
 name = "plotters"
 version = "0.3.7"
@@ -1100,6 +1182,12 @@ version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d66dc143e6b11c1eddc06d5c423cfc97062865baf299914ab64caa38182078fe"
 
+[[package]]
+name = "slab"
+version = "0.4.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a2ae44ef20feb57a68b23d846850f861394c2e02dc425a50098ae8c90267589"
+
 [[package]]
 name = "smallvec"
 version = "1.15.1"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name    = "microfetch"
-version = "0.4.11"
+version = "0.4.12"
 edition = "2024"
 
 [lib]
@@ -12,16 +12,15 @@ name = "microfetch"
 path = "src/main.rs"
 
 [dependencies]
-hotpath = { optional = true, version = "0.6.0" }
+hotpath = { optional = true, version = "0.7.5" }
 libc    = "0.2.177"
 
 [dev-dependencies]
-criterion = "0.7"
+criterion = "0.8.0"
 
 [features]
 hotpath       = [ "dep:hotpath", "hotpath/hotpath" ]
-hotpath-alloc-bytes-total = [ "hotpath/hotpath-alloc-bytes-total" ]
-hotpath-alloc-count-total = [ "hotpath/hotpath-alloc-count-total" ]
+hotpath-alloc = [ "hotpath/hotpath-alloc" ]
 hotpath-off   = [ "hotpath/hotpath-off" ]
 
 [[bench]]

README.md

@@ -43,7 +43,7 @@ on your system: it is pretty _[fast](#benchmarks)_...
 - Fast
 - Really fast
 - Minimal dependencies
-- Tiny binary (~370kb)
+- Tiny binary (~370kb [^1])
 - Actually really fast
 - Cool NixOS logo (other, inferior, distros are not supported)
 - Reliable detection of following info:
@@ -60,6 +60,9 @@ on your system: it is pretty _[fast](#benchmarks)_...
 - Did I mention fast?
 - Respects [`NO_COLOR` spec](https://no-color.org/)
 
+[^1]: With the Mold linker, which is enabled by default in the Flake package,
+    the binary size is roughly 350kb. That's nearly 20kb reduction in size :)
+
 ## Motivation
 
 Fastfetch, as its name probably hinted, is a very fast fetch tool written in C.
@@ -82,11 +85,14 @@ Nixpkgs, you are recommended to use it to utilize the binary cache properly. The
 usage of Rust _is_ nice, however, since it provides us with incredible tooling
 and a very powerful language that allows for Microfetch to be as fast as
 possible. Sure C could've been used here as well, but do you think I hate
-myself? [^1]
+myself?
 
-[^1]: Okay, maybe a little bit. One of the future goals of Microfetch is to
-    defer to inline Assembly for the costliest functions, but that's for a
-    future date and until I do that I can pretend to be sane.
+> [!IMPORTANT]
+> **Update as of November 30th, 2025**:
+>
+> Microfetch now inlines handwritten assembly for even better performance. I
+> know I previously said I do not hate myself but I'm beginning to suspect this
+> is no longer the case. Enjoy the performance benefits!
 
 ## Benchmarks
 
@@ -148,7 +154,7 @@ HOTPATH_JSON=true cargo run --features=hotpath
 To profile allocations:
 
 ```bash
-HOTPATH_JSON=true cargo run --features=hotpath,hotpath-alloc-count-total
+HOTPATH_JSON=true cargo run --features=hotpath,hotpath-alloc
 ```
 
 The JSON output can be analyzed with the `hotpath` CLI tool for detailed

flake.nix

@@ -10,9 +10,12 @@
     forEachSystem = nixpkgs.lib.genAttrs systems;
     pkgsForEach = nixpkgs.legacyPackages;
   in {
-    packages = forEachSystem (system: {
+    packages = forEachSystem (system: let
+      pkgs = pkgsForEach.${system};
+    in {
       default = self.packages.${system}.microfetch;
-      microfetch = pkgsForEach.${system}.callPackage ./nix/package.nix {};
+      microfetch = pkgs.callPackage ./nix/package.nix {};
+      microfetch-mold = pkgs.callPackage ./nix/package.nix {useMold = true;};
     });
 
     devShells = forEachSystem (system: {

nix/package.nix

@@ -1,14 +1,22 @@
 {
   lib,
-  rustPlatform,
+  stdenv,
   stdenvAdapters,
+  rustPlatform,
   llvm,
+  useMold ? stdenv.isLinux && !stdenv.hostPlatform.isAarch,
 }: let
   toml = (lib.importTOML ../Cargo.toml).package;
   pname = toml.name;
   inherit (toml) version;
+
+  # Select stdenv based on useMold flag
+  stdenv =
+    if useMold
+    then stdenvAdapters.useMoldLinker llvm.stdenv
+    else llvm.stdenv;
 in
-  rustPlatform.buildRustPackage.override {stdenv = stdenvAdapters.useMoldLinker llvm.stdenv;} {
+  rustPlatform.buildRustPackage.override {inherit stdenv;} {
     inherit pname version;
     src = let
       fs = lib.fileset;
@@ -26,7 +34,14 @@ in
 
     cargoLock.lockFile = ../Cargo.lock;
     enableParallelBuilding = true;
-    env.RUSTFLAGS = "-C link-arg=-fuse-ld=mold";
+    buildNoDefaultFeatures = true;
+    doCheck = false;
+
+    # Only set RUSTFLAGS for mold if useMold is enabled
+    env = lib.optionalAttrs useMold {
+      CARGO_LINKER = "clang";
+      RUSTFLAGS = "-C link-arg=-fuse-ld=mold";
+    };
 
     meta = {
       description = "Microscopic fetch script in Rust, for NixOS systems";

nix/shell.nix

@@ -1,27 +1,31 @@
 {
   mkShell,
+  cargo,
+  rustc,
+  mold,
+  clang,
   rust-analyzer-unwrapped,
   rustfmt,
   clippy,
-  cargo,
   taplo,
-  rustc,
   rustPlatform,
   gnuplot,
 }:
 mkShell {
+  name = "microfetch";
   strictDeps = true;
-
   nativeBuildInputs = [
     cargo
     rustc
+    mold
+    clang
 
     rust-analyzer-unwrapped
     (rustfmt.override {asNightly = true;})
     clippy
     taplo
 
-    gnuplot # For Criterion.rs plots
+    gnuplot # for Criterion.rs plots
   ];
 
   env.RUST_SRC_PATH = "${rustPlatform.rustLibSrc}";

src/lib.rs

@@ -14,7 +14,8 @@ impl UtsName {
   /// Calls `uname` syscall and returns a `UtsName` wrapper
   ///
   /// # Errors
-  /// Returns an error if the uname syscall fails
+  ///
+  /// Returns an error if the `uname` syscall fails
   pub fn uname() -> Result<Self, std::io::Error> {
     let mut uts = MaybeUninit::uninit();
     if unsafe { libc::uname(uts.as_mut_ptr()) } != 0 {

src/syscall.rs

@@ -11,11 +11,15 @@
 use std::io;
 
 /// Direct syscall to open a file
-/// Returns file descriptor or -1 on error
+///
+/// # Returns
+///
+/// File descriptor or -1 on error
 ///
 /// # Safety
 ///
 /// The caller must ensure:
+///
 /// - `path` points to a valid null-terminated C string
 /// - The pointer remains valid for the duration of the syscall
 #[inline]
@@ -65,7 +69,10 @@ pub unsafe fn sys_open(path: *const u8, flags: i32) -> i32 {
 }
 
 /// Direct syscall to read from a file descriptor
-/// Returns number of bytes read or -1 on error
+///
+/// # Returns n
+///
+/// Number of bytes read or -1 on error
 ///
 /// # Safety
 ///

src/uptime.rs

@@ -1,6 +1,6 @@
 use std::{io, mem::MaybeUninit};
 
-/// Fast integer to string conversion (no formatting overhead)
+/// Faster integer to string conversion without the formatting overhead.
 #[inline]
 fn itoa(mut n: u64, buf: &mut [u8]) -> &str {
   if n == 0 {
@@ -17,9 +17,10 @@ fn itoa(mut n: u64, buf: &mut [u8]) -> &str {
   unsafe { std::str::from_utf8_unchecked(&buf[i..]) }
 }
 
-/// Direct sysinfo syscall using inline assembly
+/// Direct `sysinfo` syscall using inline assembly
 ///
 /// # Safety
+///
 /// This function uses inline assembly to make a direct syscall.
 /// The caller must ensure the sysinfo pointer is valid.
 #[inline]