demangle not working on my symbols

[mwlon]

Maybe I'm doing something wrong, but here's an example of a symbol I can't seem to demangle:

__ZN3pco25latent_batch_decompressor32LatentBatchDecompressor$LT$U$GT$18decompress_offsets17h254da28dd89d69cbE

I just get this back:

__ZN3pco25latent_batch_decompressor32LatentBatchDecompressordecompress_offsets17h254da28dd89d69cbE

I know this function was compiled with a const generic, and I'd like to know what the value of that generic was. I produced this symbol by running cargo build --release -- --emit=asm and reading the .s file.

target: darwin aarch64
version: 0.1.23

[dtolnay]

The const generic value is not recoverable from the symbol in the default mangling scheme. You'd need to build with RUSTFLAGS='-C symbol-mangling-version=v0' to get more information in the symbols.

[mwlon]

That's good to know, but shouldn't the rest of the symbol demangle? How come it still starts with __Z...?

[dtolnay]

On my machine, that works as I would expect.

fn main() {
    let mangled = "__ZN3pco25latent_batch_decompressor32LatentBatchDecompressor$LT$U$GT$18decompress_offsets17h254da28dd89d69cbE";
    let expected = "pco::latent_batch_decompressor::LatentBatchDecompressor<U>::decompress_offsets::h254da28dd89d69cb";
    assert_eq!(rustc_demangle::demangle(mangled).to_string(), expected);
}