UEFI targets fail to compile: "LLVM ERROR: dwo only supported with ELF and Wasm"

[nicholasbishop]

The UEFI targets (x86_64-unknown-uefi, i686-unknown-uefi, and aarch64-unknown-uefi) started failing to compile in the latest nightly when using build-std, failing with "LLVM ERROR: dwo only supported with ELF and Wasm".

Code

src/main:

#![no_main]
#![no_std]

#[panic_handler]
fn panic_handler(_info: &core::panic::PanicInfo) -> ! {
    loop {}
}

#[export_name = "efi_main"]
pub extern "C" fn main(_h: *mut core::ffi::c_void, _st: *mut core::ffi::c_void) -> usize {
    0
}

.cargo/config.toml:

[unstable]
build-std = ["core", "compiler_builtins", "alloc"]
build-std-features = ["compiler-builtins-mem"]

Build:

$ cargo +nightly build --target x86_64-unknown-uefi
   Compiling core v0.0.0 (/var/home/nbishop/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core)
   Compiling rustc-std-workspace-core v1.99.0 (/var/home/nbishop/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/rustc-std-workspace-core)
LLVM ERROR: dwo only supported with ELF and Wasm
   Compiling compiler_builtins v0.1.79
LLVM ERROR: dwo only supported with ELF and Wasm
error: could not compile `rustc-std-workspace-core`
warning: build failed, waiting for other jobs to finish...
error: could not compile `core`
LLVM ERROR: dwo only supported with ELF and Wasm
error: could not compile `compiler_builtins`

cargo-bisect-rustc output

searched nightlies: from nightly-2022-08-25 to nightly-2022-08-27
regressed nightly: nightly-2022-08-27
searched commit range: 7480389...c07a8b4
regressed commit: 450e99f

bisected with cargo-bisect-rustc v0.6.4

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc -- build --target x86_64-unknown-uefi 

CC @davidtwco since bisect pointed to #98051

[kennystrawnmusic]

Can confirm. Definitely needs to be looked into by the team — @phil-opp can you reproduce this?

[nicholasbishop]

I see in https://github.com/rust-lang/rust/pull/98051/files#diff-e8d72f87be1eb954600ca7d27ce0fdd7360fe43e393c5bb0d73e226f11abc67d that debuginfo_kind: DebuginfoKind::Pdb is set in windows_msvc_base. I think that needs to be added in https://github.com/rust-lang/rust/blob/master/compiler/rustc_target/src/spec/uefi_msvc_base.rs, or maybe directly in msvc_base?

I tested this out locally by using a custom target JSON that matches x86_64-unknown-uefi except adds "debuginfo-kind": "pdb", and that seems to fix the bug.