WASI: Cannot open paths with nightly >= 2021-03-11 when linked with LLD 11.1

[abbec]

I have code opening a path like std::fs::read("/absolute/path.txt") in WASI. All the surrounding code stays the same but when I upgrade nightly from 2021-03-10 to 2021-03-11 it does not work anymore.

Version details:

# opening a path with leading "/" does _NOT_ work
rustc 1.52.0-nightly (f98721f88 2021-03-10)
binary: rustc
commit-hash: f98721f886ab52d32d622ad0a46216ad03f3e525
commit-date: 2021-03-10
host: x86_64-apple-darwin
release: 1.52.0-nightly

# opening a path with leading "/" _DOES_ work
rustc 1.52.0-nightly (3a5d45f68 2021-03-09)
binary: rustc
commit-hash: 3a5d45f68cadc8fff4fbb557780f92b403b19c19
commit-date: 2021-03-09
host: x86_64-apple-darwin
release: 1.52.0-nightly
LLVM version: 12.0.0

Looking at the history, the only thing I can see that looks WASI-related is this but I have no idea here and any help would be appreciated!

EDIT: This description turned out to be somewhat incorrect, see below for a good repro case.

[abbec]

I was wrong, actually it does not work at all on nightly 2021-03-11 and onwards (I tested nightly 2021-05-11 with the same result), with or without the leading "/":

failed to find a pre-opened file descriptor through which "relative/path.txt" could be opened

and

failed to find a pre-opened file descriptor through which "/absolute/path.txt" could be opened

whereas on nightly 2021-03-10 the same code works fine both with and without the leading "/".

[apiraino]

hi @abbec thanks for filing a report. Do you imply that even a snippet like this returns that error?

use std::fs;
fn repro() {
    fs::read("/absolute/path.txt").unwrap();
}
fn main() {
    repro();
}

Can you attach a small but fully actionable and reproducible snippet (along with the command to compile)? There might be more to investigate and that would be useful. Thanks!

[abbec]

No, that does work and I am using my own version of wasilibc that I am linking against (which is the same version as the one currently used by std) but the strange thing is that it does work on one date and the same code stops working on the next.

[abbec]

Seems to have something to do with using a custom linker and using the external wasilibc, I will investigate more, still something needs to have changed between these two versions.

[abbec]

Seems to be only when using a custom linker (LLVM 11 in this case). Any tips for debugging would be very appreciated!

[apiraino]

Which command and rustc flags do you use to compile the sources? Also, do you get an actual error stack? If yes, can you expand that error with RUST_BACKTRACE=full? Are you able to test against the latest LLVM 12?