Subsecond: Using `mold` requires a system-wide symlink

[janhohenheim]

Problem

When using mold, it seems like ld is still used for some reason:

Note that my app runs after doing

cd /usr/bin
mv ld ld-real
ln -s mold ld

Steps To Reproduce

Steps to reproduce the behavior:

• Run cargo install dioxus-cli --git https://github.com/DioxusLabs/dioxus --rev b2bd1f48d434becfff9f0ea390ad8ef46996300a
• Clone https://github.com/TheBevyFlock/bevy_simple_subsecond_system
• Add the following to your ~/.cargo/config.toml:

  [target.x86_64-unknown-linux-gnu]
  # linker = "clang"
  rustflags = [
    "link-arg=-fuse-ld=mold",
  ]

  • linker is commented out due to Subsecond fails when linker is specified #4193, so I instead symlinked cc to clang:

    readlink -f $(which cc)
    > /usr/lib64/llvm20/bin/clang-20

• Run dx serve --hot-patch --example minimal

Expected behavior

The app to run

Environment:

• Dioxus version: dioxus 0.7.0-alpha.0 (48e925f)
• Rust version: rustc 1.89.0-nightly (ce7e97f73 2025-05-11)
• OS info: Fedora release 42 (Adams)
• App platform: Desktop Linux

[janhohenheim]

Update: this workaround breaks down on changes. Hot-patching works, but recompiling after changes gives me

05:19:13 [dev] Failed to generate fat binary: mold: warning: unknown command line option: -znostart-stop-gc
mold: fatal: /home/hhh/.cargo/global-target/x86_64-unknown-linux-gnu/debug/libdeps-7970178b.a: unknown file type
cc: error: linker command failed with exit code 1 (use -v to see invocation)
05:19:13 [dev] Build failed: Failed to write main executable

[janhohenheim]

Fixed by #4222