cargo-miri does not work with sccache

[TriplEight]

Must be related to #573

<>build log<>

$ cargo -vV
cargo 1.45.0-nightly (cb06cb269 2020-05-08)
release: 1.45.0
commit-hash: cb06cb2696df2567ce06d1a39b1b40612a29f853
commit-date: 2020-05-08
$ rustc -vV
rustc 1.45.0-nightly (75e1463c5 2020-05-13)
binary: rustc
commit-hash: 75e1463c52aaea25bd32ed53c73797357e561cce
commit-date: 2020-05-13
host: x86_64-unknown-linux-gnu
release: 1.45.0-nightly
LLVM version: 9.0
$ rustup show
Default host: x86_64-unknown-linux-gnu
rustup home:  /usr/local/rustup
installed toolchains
--------------------
stable-x86_64-unknown-linux-gnu
nightly-2020-05-14-x86_64-unknown-linux-gnu (default)
nightly-x86_64-unknown-linux-gnu
installed targets for active toolchain
--------------------------------------
wasm32-unknown-unknown
x86_64-unknown-linux-gnu
active toolchain
----------------
nightly-2020-05-14-x86_64-unknown-linux-gnu (default)
rustc 1.45.0-nightly (75e1463c5 2020-05-13)
$ bash --version
GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
$ cargo miri --version; rustup component add rust-src; pushd core; cargo miri test --verbose -- -- storage2; popd
miri 0.1.0 (10419b3 2020-05-11)
info: downloading component 'rust-src'
info: installing component 'rust-src'
/builds/parity/ink/core /builds/parity/ink
Running `"/usr/local/rustup/toolchains/nightly-2020-05-14-x86_64-unknown-linux-gnu/bin/cargo" "install" "xargo" "-f"` to install a recent enough xargo.
    Updating crates.io index
 Downloading crates ...
  Downloaded xargo v0.3.20
  Installing xargo v0.3.20
 Downloading crates ...
  Downloaded addr2line v0.12.1
  Downloaded tempdir v0.3.7
  Downloaded walkdir v1.0.7
  Downloaded num-traits v0.2.11
  Downloaded serde v0.8.23
  Downloaded rand v0.4.6
  Downloaded object v0.19.0
  Downloaded libc v0.2.70
  Downloaded rustc-serialize v0.3.24
  Downloaded rustc-demangle v0.1.16
  Downloaded remove_dir_all v0.5.2
  Downloaded num-traits v0.1.43
  Downloaded dtoa v0.2.2
  Downloaded gimli v0.21.0
  Downloaded fs2 v0.4.3
  Downloaded error-chain v0.7.2
  Downloaded dirs v1.0.5
  Downloaded cfg-if v0.1.10
  Downloaded backtrace v0.3.48
  Downloaded autocfg v1.0.0
  Downloaded toml v0.2.1
  Downloaded rustc_version v0.1.7
  Downloaded serde_json v0.8.6
  Downloaded same-file v0.1.3
  Downloaded itoa v0.1.1
  Downloaded semver v0.1.20
   Compiling libc v0.2.70
   Compiling autocfg v1.0.0
   Compiling gimli v0.21.0
   Compiling cfg-if v0.1.10
   Compiling object v0.19.0
   Compiling rustc-demangle v0.1.16
   Compiling xargo v0.3.20
   Compiling same-file v0.1.3
   Compiling semver v0.1.20
   Compiling serde v0.8.23
   Compiling itoa v0.1.1
   Compiling rustc-serialize v0.3.24
   Compiling remove_dir_all v0.5.2
   Compiling dtoa v0.2.2
   Compiling walkdir v1.0.7
   Compiling num-traits v0.2.11
   Compiling rustc_version v0.1.7
   Compiling rand v0.4.6
   Compiling dirs v1.0.5
   Compiling fs2 v0.4.3
   Compiling num-traits v0.1.43
   Compiling tempdir v0.3.7
   Compiling serde_json v0.8.6
   Compiling addr2line v0.12.1
   Compiling toml v0.2.1
   Compiling backtrace v0.3.48
   Compiling error-chain v0.7.2
    Finished release [optimized] target(s) in 24.83s
  Installing /usr/local/cargo/bin/xargo
  Installing /usr/local/cargo/bin/xargo-check
   Installed package `xargo v0.3.20` (executables `xargo`, `xargo-check`)
error: failed to run `rustc` to learn about target-specific information
Caused by:
  process didn't exit successfully: `sccache /usr/local/rustup/toolchains/nightly-2020-05-14-x86_64-unknown-linux-gnu/bin/miri - --crate-name ___ --print=file-names --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg` (exit code: 2)
--- stderr
error: failed to execute compile
caused by: Compiler not supported: "error: Unrecognized option: \'E\'\n\n"
error: `"/usr/local/rustup/toolchains/nightly-2020-05-14-x86_64-unknown-linux-gnu/bin/cargo" "check" "--release" "--manifest-path" "/tmp/xargo.fvDL6G47j2QU/Cargo.toml" "--target" "x86_64-unknown-linux-gnu" "-p" "std"` failed with exit code: Some(101)
   0: error_chain::make_backtrace
   1: <error_chain::State as core::default::Default>::default
   2: <std::process::Command as xargo::extensions::CommandExt>::run
   3: xargo::sysroot::build
   4: xargo::sysroot::update
   5: xargo::main_inner
   6: std::rt::lang_start::{{closure}}
   7: std::rt::lang_start_internal::{{closure}}
             at /rustc/75e1463c52aaea25bd32ed53c73797357e561cce/src/libstd/rt.rs:52
      std::panicking::try::do_call
             at /rustc/75e1463c52aaea25bd32ed53c73797357e561cce/src/libstd/panicking.rs:297
      std::panicking::try
             at /rustc/75e1463c52aaea25bd32ed53c73797357e561cce/src/libstd/panicking.rs:274
      std::panic::catch_unwind
             at /rustc/75e1463c52aaea25bd32ed53c73797357e561cce/src/libstd/panic.rs:394
      std::rt::lang_start_internal
             at /rustc/75e1463c52aaea25bd32ed53c73797357e561cce/src/libstd/rt.rs:51
   8: main
   9: __libc_start_main
  10: _start
fatal error: Failed to run xargo

so in CI, where I use sccache everywhere by default it helps me to

unset RUSTC_WRAPPER
cargo miri setup # to avoid if it asks for sudden new dependencies
cargo miri test ...

[bjorn3]

process didn't exit successfully: sccache /usr/local/rustup/toolchains/nightly-2020-05-14-x86_64-unknown-linux-gnu/bin/miri - --crate-name ___ --print=file-names --crate-type bin --crate-type rlib --crate-type dylib --crate-type cdylib --crate-type staticlib --crate-type proc-macro --print=sysroot --print=cfg (exit code: 2)
[...]
caused by: Compiler not supported: "error: Unrecognized option: 'E'\n\n"

The problem here is that sccache doesn't support using miri as compiler. It only checks for rustc and clippy-driver as rustc compilers. In all other cases it assumes that it is a C compiler and passes -E as argument, which miri doesn't support.

https://github.com/mozilla/sccache/blob/f50207525810c12f9dbad2b9e92892d055b1b38a/src/compiler/compiler.rs#L906

https://github.com/mozilla/sccache/blob/f50207525810c12f9dbad2b9e92892d055b1b38a/src/compiler/compiler.rs#L1052

[RalfJung]

Must be related to #573

I don't think so. That is us overwriting RUSTC_WRAPPER. The error you see happens when we call xargo, which is before we do anything with RUST_WRAPPER.

I have no experience with sccache, so I am not sure if the better solution is to add "miri" as a rustc name in sccache, or to unset RUSTC_WRAPPER in cargo miri. We already effectively unset it for the actual project compilation anyway, just not for xargo.

[RalfJung]

I proposed a fix in #1426.
@TriplEight would that work for you, or do you require Miri builds to actually be sccache'd? I'm afraid I wouldn't know what it takes to achieve that.

[TriplEight]

Thanks for mentioning!
It would be really great to have it cached (both with sccache and CARGO_TARGET_DIR), because it takes a really long time on heavy projects.

But currently it seems to break my CI completely.
The setup is: I have everything needed installed in docker image and CI just checkouts the commit and runs the cargo command. It uses sccache and CARGO_TARGET_DIR. And what happened is I've added miri, xargo and rust-src to the CI docker image and started having failures all over CI (not just in miri job).

I believe this fix is going to fix what I've just described. Can share logs and whatever code is needed, but tomorrow.

[RalfJung]

It would be really great to have it cached (both with sccache and CARGO_TARGET_DIR), because it takes a really long time on heavy projects.

What is taking long is likely the actual evaluation -- as in, running the program. I don't think it makes any sense to cache that.^^

CARGO_TARGET_DIR is a separate problem, see #1311.