Fail to build after new rustc pipelining compilation feature

[tesuji]

Basic information

sccache version: 0.2.8
OS: Debian GNU/Linux 9.9 (stretch) (4.9.0-8-amd64 #1 SMP Debian 4.9.144-3.1 (2019-02-19) x86_64 GNU/Linux)
cargo version: cargo 1.36.0-nightly (c4fcfb725 2019-05-15)
rustc version: rustc 1.36.0-nightly (6afcb5628 2019-05-19)

Reproducible steps

% rm -rf ~/.cache/sccache
% export RUSTC_WRAPPER=sccache
% export CARGO_BUILD_PIPELINING=true 
% git clone https://github.com/m4b/goblin.git
% cd goblin
% cargo build
% cargo clean
% cargo build
   Compiling proc-macro2 v0.4.30
   Compiling semver-parser v0.7.0
   Compiling unicode-xid v0.1.0
   Compiling syn v0.15.34
   Compiling cfg-if v0.1.9
   Compiling plain v0.2.3
   Compiling log v0.4.6
sccache: encountered fatal error
sccache: error : Failed to open file for hashing: "/home/lzutao/forked/rust/goblin/target/debug/deps/libcfg_if-e6b10e8042cb123a.rmeta"
sccache:  cause: Failed to open file for hashing: "/home/lzutao/forked/rust/goblin/target/debug/deps/libcfg_if-e6b10e8042cb123a.rmeta"
sccache:  cause: No such file or directory (os error 2)
error: Could not compile `log`.

Caused by:
  process didn't exit successfully: `sccache rustc --crate-name log /home/lzutao/.cargo/registry/src/github.com-1ecc6299db9ec823/log-0.4.6/src/lib.rs --color always --crate-type lib --emit=dep-info,metadata,link -C debuginfo=2 -C metadata=aa0fc3947c9b41c0 -C extra-filename=-aa0fc3947c9b41c0 --out-dir /home/lzutao/forked/rust/goblin/target/debug/deps -L dependency=/home/lzutao/forked/rust/goblin/target/debug/deps --extern cfg_if=/home/lzutao/forked/rust/goblin/target/debug/deps/libcfg_if-e6b10e8042cb123a.rmeta --cap-lints allow --error-format=json --json-rendered=termcolor -Zunstable-options -Zemit-artifact-notifications` (exit code: 254)
warning: build failed, waiting for other jobs to finish...
error: build failed

[chmanchester]

This is closely related to #436: when rustc emits an rmeta file sccache doesn't always handle that correctly.

[tesuji]

I don't think the problem has been fixed. It still failed on my side
with the lasted commit: 806ce30

[chmanchester]

Does the issue persist after removing ~/.cache/sccache? I'm no longer able to reproduce the issue with the most recent commit applied.

[tesuji]

Hmm. It's weird that I cannot reproduce it anymore.
Maybe some problem with the hard drive.
Anyway, if I find any reproducible cases, I'll open a new issue.

Thanks for the work on this!