`rustc_driver.dll` not found on Windows

[BD103]

I followed the installation guide on Windows, but running the linter throws an error:

$ bevy_lint
error: process didn't exit successfully: `\\?\C:\Users\USER\.cargo\bin\bevy_lint_driver.exe C:\Users\USER\.rustup\toolchains\nightly-2024-11-14-aarch64-pc-windows-msvc\bin\rustc.exe -vV` (exit code: 0xc0000135, STATUS_DLL_NOT_FOUND)
Check failed: exit code: 101.

I theorize that rustup run isn't setting up the path correctly, but it still needs further investigation.

[BD103]

Originally discovered on Discord.

[BD103]

I was able to confirm that rustup run isn't correctly configuring the path, because the following works:

# Switch to the directory that contains `rustc_driver.dll`
cd C:\Users\USER\.rustup\toolchains\nightly-2024-11-14-aarch64-pc-windows-msvc\bin
# Run the lint driver, which should print the help screen
bevy_lint_driver rustc --help

When bevy_lint_driver is run elsewhere, nothing is printed (presumably because the DLL could not be loaded).

[BD103]

I was able to verify that rustup run doesn't configure the path (in a more straightforward way) by compiling the following program as pathfinder.exe:

fn main() {
    println!("PATH={}", std::env::var("PATH").unwrap());
}

Then, I compared the output of the following two commands:

> .\pathfinder.exe
PATH=C:\Program Files\Parallels\Parallels Tools\Applications;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Users\USER\.cargo\bin;C:\Users\USER\AppData\Local\Microsoft\WindowsApps;
> rustup run nightly-2025-01-09 .\pathfinder.exe
PATH=C:\Program Files\Parallels\Parallels Tools\Applications;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Users\USER\.cargo\bin;C:\Users\USER\AppData\Local\Microsoft\WindowsApps;

Diff view:

- PATH=C:\Program Files\Parallels\Parallels Tools\Applications;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Users\USER\.cargo\bin;C:\Users\USER\AppData\Local\Microsoft\WindowsApps;
+ PATH=C:\Program Files\Parallels\Parallels Tools\Applications;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Users\USER\.cargo\bin;C:\Users\USER\AppData\Local\Microsoft\WindowsApps;

Interestingly, the path is configured correctly when I run pathfinder.exe using cargo run:

> cargo run
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.01s
     Running `.\pathfinder.exe`
PATH=C:\Users\USER\Downloads\pathfinder\target\debug\deps;C:\Users\USER\Downloads\pathfinder\target\debug;C:\Users\USER\.rustup\toolchains\stable-aarch64-pc-windows-msvc\lib\rustlib\aarch64-pc-windows-msvc\lib;C:\Program Files\Parallels\Parallels Tools\Applications;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.0\;C:\Windows\System32\OpenSSH\;C:\Users\USER\.cargo\bin;C:\Users\USER\AppData\Local\Microsoft\WindowsApps;

[BD103]

I found the issue! Due to rust-lang/rustup#3703, Rustup no longer modifies the PATH on Windows because it prevented sub-invocations of cargo and rustc from going through their proxy. There was a call for testing related to this, but it was announced before the linter was ever created. Because I don't use Windows frequently¹, I never caught the issue.

We can fix this by setting RUSTUP_WINDOWS_PATH_ADD_BIN=1:

> set RUSTUP_WINDOWS_PATH_ADD_BIN=1
> rustup run nightly-2025-01-09 .\bevy_lint.exe

Footnotes

1. Though I did use a virtual machine to debug this issue. ↩

[BD103]

I opened #281 to fix this issue. I also opened rust-lang/rustup#4196 to make RUSTUP_WINDOWS_PATH_ADD_BIN a little more visible in Rustup's documentation.