LLVM ERROR: Unexpected anonymous function when writing summary

[japaric]

When compiling the compiler_builtins crate for any of the thumb targets in release mode and with debuginfo enabled. Without debuginfo the build succeeds (we are testing this by building rust-std for the thumb targets). This doesn't affect the ARM Linux targets.

STR

$ cp -r $(rustc --print sysroot)/lib/rustlib/src/rust/src/ src && cd $_

$ cd libcompiler_builtins

$ cat >>Cargo.toml <<'EOF'
[profile.release]
debug = true
EOF

$ cargo build --target thumbv7m-none-eabi --release
LLVM ERROR: Unexpected anonymous function when writing summary

Metadata

$ rustc -V
rustc 1.28.0-nightly (e3bf634e0 2018-06-28)

Needs bisecting

cc @alexcrichton

[Mark-Simulacrum]

$ cargo-bisect-rustc --start 56714acc5eb0687ed9a7566fdebe5528657fc5b3 --target thumbv7m-none-eabi --prompt --test-dir case/src/libcompiler_builtins --by-commit  -- build --target thumbv7m-none-eabi --release

searched toolchains 56714acc5eb0687ed9a7566fdebe5528657fc5b3 through 96b47337d9deebdb9cbca909e7772672062021e5
regression in e1151c9819cca90e511f60757297629177272d16

e1151c9 - #49479 - cc @nagisa @nox

[nikic]

Could this be hitting the case where linking is performed without thinlto, but bitcode is still being written through thinlto buffers? It might be worth trying to apply these changes and see if it fixes the issue: https://github.com/rust-lang/rust/pull/51007/files#diff-a3c60982b42eac1d2e3fd67f4d562ae8R550

[nagisa]

Yeah, the error message definitely sounds related to thinlto. At least "summary" is a thinlto concept.

That being said, it doesn’t seem like thinlto is disabled anywhere in the original report, so…

[agalakhov]

I just tried it with "-Z thinlto=no", and it does NOT help.

[aribeironovaes]

Hi @japaric ,

Did you figure our how to fix this issue?
I'm trying to run cortex-m-quickstart on a STM32L475 and I'm getting Stuck on the LLVM ERROR: Unexpected anonymous function when writing summary error if debug = true.

Can you let me know if you could successfully run the sample on this version of Cortex M4?

Thanks lot in advance,

Angelo Ribeiro.

[maximevince]

Same problem here! Any solution or workaround known?

[nikic]

Running with -C lto=thin worked for me, so I think my general guess in #51947 (comment) was right -- unfortunately the linked patch has landed in the meantime and has not fixed the issue. rustc is being run with --crate-type lib --emit=dep-info,link here, I'll have to check what exactly that means for bitcode emission.

[nikic]

Here is a reproducer without the compiler_builtins/thumb dependency:

#![feature(linkage)]
  
#[linkage = "weak"]
pub fn fn1(a: u32, b: u32, c: u32) -> u32 {
    a + b + c
}

#[linkage = "weak"]
pub fn fn2(a: u32, b: u32, c: u32) -> u32 {
    a + b + c
}

Compiled with --crate-type=rlib -O this produces the anon function error.