rustup run doesn't setup the dylib path on windows

[Nadrieril]

Verification

• I searched for recent similar issues at https://github.com/rust-lang/rustup/issues?q=is%3Aissue+is%3Aopen%2Cclosed and found no duplicates.
• I am on the latest version of Rustup according to https://github.com/rust-lang/rustup/tags and am still able to reproduce my issue.

Problem

Hi! I am developping a rustc driver. I make sure to always call it as rustup run my-driver, which works on Mac and Linux: both the toolchain binaries and the rustc_driver.so are accessible so my program runs well. On Windows however, calling the driver fails with "rustc_driver.dll not found".

And indeed, as far as I can tell rustup run only attempts to set up loader paths on macos and linux:

rustup/src/toolchain.rs

Line 178 in 895a43a

fn set_ldpath(&self, cmd: &mut Command) {

I've seen related issues (#765, #932, #1152), but they're not exactly the same problem.

Steps

1. Install the required rustup components: rustup component add --toolchain nightly rust-src rustc-dev llvm-tools-preview;
2. Make a minimal binary crate that dynamically links to rustc-internal crates:

#![feature(rustc_private)]
extern crate rustc_driver;
fn main() {
    println!("Hello, World!");
}

3. cargo +nightly build
4. Run the resulting binary on Windows with rustup run nightly path\to\test-crate.exe

Possible Solution(s)

I can't test myself because I don't own a Windows machine, but a user reports that adding the lib path (e.g. C:\Users\Administrator\.rustup\toolchains\nightly-2024-10-23-x86_64-pc-windows-msvc\lib\rustlib\x86_64-pc-windows-msvc\lib), to PATH (instead of LD_LIBRARY_PATH) works. This seems confirmed by a quick google search.

Notes

The reproducing details (OS version etc) are not precise because I'm reporting on behalf of a user. If you can't reproduce on your Windows machine I'll ask for more details.

Rustup version

rustup 1.27.1

Installed toolchains

nightly

OS version

Windows ???

[rami3l]

@Nadrieril Thanks for your report.

You might need to set RUSTUP_WINDOWS_PATH_ADD_BIN=1 to make it work. If this is the case then this is a duplicate of #3825.

[zjp-CN]

Thanks for the link. RUSTUP_WINDOWS_PATH_ADD_BIN=1 solves the problem for now.

Also related to these links:

• Document RUSTUP_WINDOWS_PATH_ADD_BIN #4196
• Change default for RUSTUP_WINDOWS_PATH_ADD_BIN #3703

But I don't see why PATH can't be appended with libdir by rustup, saying adding C:\Users\Administrator\.rustup\toolchains\nightly-2024-10-23-x86_64-pc-windows-msvc\lib\rustlib\x86_64-pc-windows-msvc\lib to PATH.

I indeed noticed the RUSTUP_WINDOWS_PATH_ADD_BIN code and comment in rustup. At that time, I think it just adds a bin dir rather than lib dir, which wouldn't have helped.

Update: after scanning
C:\Users\Administrator\.rustup\toolchains\nightly-2024-10-23-x86_64-pc-windows-msvc\bin and
C:\Users\Administrator\.rustup\toolchains\nightly-2024-10-23-x86_64-pc-windows-msvc\lib\rustlib\x86_64-pc-windows-msvc\lib, it seems the latter contains more deps dlls which might cause troubles? Can rustup create a dir only containing rust dll libs, and add it to PATH?

[rami3l]

@zjp-CN Thanks for your feedback! Let's continue the discussion over there in the main issue then.

[Nadrieril]

Oh amazing, I didn't expect this variable would work, glad it does.