[E0514] error message not clear

[MagaTailor]

I was trying to cross-compile something, and even though, the identically named down to the hash (compatible?), std crate for the cross arch had come from the same minor version (rustc 1.6.0-dev) I still got the error:

 hello.rs:1:1: 1:1 error: the crate `std` has been compiled with rustc 1.6.0-dev, which is incompatible with this version of rustc [E0514]

What is required for the crates to be compatible then? The exact commit hash of the rust compilers as well?

If so, this issue could be about something else too - building from a full source snapshot (instead of git clones) doesn't put the hash info into the binary.

[sfackler]

The compilers must have been built from the same commit.

[MagaTailor]

Strange that it's not printing the hash if it's still able to compare against it.

[ticki]

Try to run cargo clean

[MagaTailor]

Fresh from the reddit thread, eh?
It's not that issue.

EDIT:
https://www.reddit.com/r/rust/comments/3wic4c/error_the_crate_regex_has_been_compiled_with_an/

[ticki]

Reddit thread?

[arielb1]

What compilers were you using?

[MagaTailor]

Those were 1.6 nightlies for armhf (from rustbuild) and i686 (mine) architectures roughly from the same day - hence the matching crate names.

[arielb1]

Apparently the nightlies are built with different values of CFG_VERSION. Could @alexcrichton investigate?

[arielb1]

The CFG_VERSION is visible by doing strings $RLIB_FILE_CREATED_BY_RUSTC | grep "rustc 1[.]", or by rustc --version.

[alexcrichton]

I guess this may depend on the string being compared, the nightly compilers have the version string ending with -nightly and from-source builds use -dev by default (configurable either way of course).

I wonder if perhaps this check should just compare commit revisions?

[MagaTailor]

I can confirm I got it working in both directions using 1.5.0-dev (after building from the same snapshot on both architectures) - rustc -vV doesn't include the hash info nor build date though.

[MagaTailor]

I'd like to suggest including the commit info in the full source snapshots so that it can be parsed by the build scripts and rustc -vV doesn't end up like this:

rustc 1.8.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: arm-unknown-linux-gnueabihf
release: 1.8.0-dev

[MagaTailor]

The original issue has turned out to be about something else - fully compatible crates were being rejected for the sole reason CFG_VERSION was different. Otherwise, the message would have been crystal clear.

In other words, it's not possible to pick up crates from rust-lang and use them in your own compiler built from tarball source, meaning #30622 shouldn't close this.

[MagaTailor]

#33286