Failure to compile unit tests for procedural macros on stable-x86_64-pc-windows-gnu

[quixoticaxis]

I tried the following code.

In the proc-macro nested crate macros-derive:

use proc_macro::TokenStream;

#[proc_macro_derive(NoDerive)] // does nothing
pub fn derive_print_type(_input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    TokenStream::new()
}

#[cfg(test)]
mod tests {

    #[test]
    fn test() {}
}

In the main crate:

use macros_derive::NoDerive;

fn main() {
    _ = S;
}

#[derive(NoDerive)]
struct S;

I expected to see this happen: cargo test runs to completion.

Instead, compilation of the test target fails:

Compiling macros v0.1.0 (…\proc-macro failure\macros)
Compiling macros-derive v0.1.0 (…\proc-macro failure\macros\derive)
error: Error calling dlltool 'dlltool.exe': program not found

error: could not compile macros-derive (lib test) due to 1 previous error
warning: build failed, waiting for other jobs to finish...

If I add dlltool from self-contained folder (from inside the toolchain folder) to PATH, the compilation fails with:

error: Dlltool could not create import library

Stable version:

rustc 1.80.0 (0514789 2024-07-21)
binary: rustc
commit-hash: 0514789
commit-date: 2024-07-21
host: x86_64-pc-windows-gnu
release: 1.80.0
LLVM version: 18.1.7

Nightly version (same result):

rustc 1.82.0-nightly (ca5d25e 2024-08-09)
binary: rustc
commit-hash: ca5d25e
commit-date: 2024-08-09
host: x86_64-pc-windows-gnu
release: 1.82.0-nightly
LLVM version: 19.1.0

[quixoticaxis]

I've found out (looking at #103939) that it is possible to install MSYS2, then install clang for MSYS2 and use the clang's executable. (I did not test it for now. ) Is it the currently optimal workaround or are there easier ways to make things work with GNU toolchain on Windows?

[quixoticaxis]

I tried different stable versions: seems like the tests compiled but failed with STATUS_DLL_NOT_FOUND up to 1.77, and failed to compile from 1.78 onwards.

I also found the version that worked out of the box. The last stable version I found to support proc-macro tests on Windows GNU toolchain is 1.43. Even tried a real test with proc-macro2 (used 0.4 version), works fine.

[denniskempin]

We are running into the same issue. Reproduced this on a fresh windows VM with serde_derive, but it seems to happen on every proc macro crate we tried when running cargo test with the -gnu toolchain.

It works on 1.77.2:

PS C:\Users\denniskempin\Downloads\serde\serde_derive> cargo +1.77.2 test --no-run
   ...
    Finished test [unoptimized + debuginfo] target(s) in 23.92s
  Executable unittests src\lib.rs (C:\Users\denniskempin\Downloads\serde\target\debug\deps\serde_derive-64ff7c3b497d1e75.exe)

Fails on 1.78.0

PS C:\Users\denniskempin\Downloads\serde\serde_derive> cargo +1.78.0 test --no-run
   Compiling proc-macro2 v1.0.93
   Compiling unicode-ident v1.0.17
   Compiling serde_derive v1.0.217 (C:\Users\denniskempin\Downloads\serde\serde_derive)
   Compiling serde v1.0.217 (C:\Users\denniskempin\Downloads\serde\serde)
   Compiling quote v1.0.38
   Compiling syn v2.0.98
error: Error calling dlltool 'dlltool.exe': program not found

error: could not compile `serde_derive` (lib test) due to 1 previous error

dlltool.exe is part of the rust-mingw component, so we tried fixing up the path manually:

PS C:\Users\denniskempin\Downloads\serde\serde_derive> $env:Path += ';C:\Users\denniskempin\.rustup\toolchains\1.78.0-x86_64-pc-windows-gnu\lib\rustlib\x86_64-pc-windows-gnu\bin\self-contained'
PS C:\Users\denniskempin\Downloads\serde\serde_derive> cargo +1.78.0 test --no-run
   Compiling serde_derive v1.0.217 (C:\Users\denniskempin\Downloads\serde\serde_derive)
error: Dlltool could not create import library with C:\Users\denniskempin\.rustup\toolchains\1.78.0-x86_64-pc-windows-gnu\lib\rustlib\x86_64-pc-windows-gnu\bin\self-contained\dlltool.exe -d C:\Users\DENNIS~1\AppData\Local\Temp\2\rustcfhXwSO\api-ms-win-core-synch-l1-2-0.def -D api-ms-win-core-synch-l1-2-0.dll -l C:\Users\DENNIS~1\AppData\Local\Temp\2\rustcfhXwSO\api-ms-win-core-synch-l1-2-0.lib -m i386:x86-64 -f --64 --no-leading-underscore --temp-prefix C:\Users\DENNIS~1\AppData\Local\Temp\2\rustcfhXwSO\api-ms-win-core-synch-l1-2-0.dll:

       C:\Users\denniskempin\.rustup\toolchains\1.78.0-x86_64-pc-windows-gnu\lib\rustlib\x86_64-pc-windows-gnu\bin\self-contained\dlltool.exe: CreateProcess

error: could not compile `serde_derive` (lib test) due to 1 previous error

Unfortunately I have not found a way to get any more detailed logging out of this than CreateProcess. Briefly looking at dlltool, it seems to be trying to call both "as.exe" an "ld.exe". "ld" exists in the same path but "as" does not. So maybe that's the issue?