building rust component code fails with error: could not read vendor path

[lucifer8851]

Steps to reproduce:

• Build the Rust Compiler (https://github.com/ivmarkov/rust)
• toolchain setup + set XARGO_RUST_SRC with export XARGO_RUST_SRC=`rustc --print sysroot`/lib/rustlib/src/rust/library
• go to rust-esp32-std-hello/rust folder and execute xargo build --release

It fails with the following error
error: could not read vendor path

[ivmarkov]

Can you create an empty vendor directory in the root of the rust folder where you checked out https://github.com/ivmarkov/rust and then try compiling the app again (no need to rebuild the compiler)?

Let me know the outcome.

[AdityaHPatwardhan]

Hey @ivmarkov Thanks for the suggestion, I was able to resolve the could not read vendor path error by creating a pseudo vendor directory
But after resolving that the build still fails with a few unresolved imports.

error[E0432]: unresolved import `core::iter`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:43:13
   |
43 |         use core::iter;
   |             ^^^^^^^^^^ no `iter` in the root

error[E0432]: unresolved import `core::ops`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:45:13
   |
45 |         use core::ops;
   |             ^^^^^^^^^ no `ops` in the root

error[E0432]: unresolved import `core::option`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:47:13
   |
47 |         use core::option;
   |             ^^^^^^^^^^^^ no `option` in the root

error[E0432]: unresolved import `core::ffi`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:55:13
   |
55 |         use core::ffi;
   |             ^^^^^^^^^ no `ffi` in the root

error[E0432]: unresolved import `core::fmt`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:57:13
   |
57 |         use core::fmt;
   |             ^^^^^^^^^ no `fmt` in the root

error[E0432]: unresolved import `core::hash`
  --> /Users/flying_raijin/.cargo/registry/src/git.luolix.top-1ecc6299db9ec823/libc-0.2.80/src/lib.rs:59:13

Any suggestion on what I might do to resolve them ?
thanks.

[ivmarkov]

That's strange. Looks as if the core crate that xargo compiles is broken.

In any case, I found an issue in .cargo/config I've fixed now.
Please try the following:

1. Pull latest from the repo
2. xargo clean
3. rm -rf ~/.cargo/registry/
4. rm -rf ~/.cargo/git/
5. xargo build --release

Also: looks as if you are building on Mac? Haven't tried there, only Linux. In theory, there should be no difference, but then who knows. Let me try on Mac, but mind you - rebuilding the whole toolchain & all might take a while...

[ivmarkov]

OK, so on a completely pristine Mac (only brew, Xcode and git installed):

• The rust xtensa+STD toolchain compiles just fine by following the instructions (only had to do brew install cmake and brew install ninja for the LLVM to build; your rustup link xtensa ... command would be slightly different on Mac of course, as you've built an x86_64-apple-darwin target instead of x86_64-unknown-linux-gnu but I guess I'm becoming Mr Obvious here).
• The rust-esp32-std-hello app also compiles fine.

Disclaimers:

• I've only checked with the latest rust-esp32-std-hello version (with the fixes to .cargo/config applied)
• Everything (rustup and then xargo) was installed prior to/after the toolchain build
• Obviously, i've started with completely empty ~/.cargo/registry and ~./cargo/git directories. So perhaps wiping those out as I suggested above might help

[ivmarkov]

Huh. Kind of strange. On Mac it also did not even complain about the "vendor" directory.
Even stranger that the stable compiler on Mac (the one I used for building the xtensa+STD toolchain) is the same as the one on Lunux:
stable-x86_64-apple-darwin unchanged - rustc 1.48.0 (7eac88abb 2020-11-16)

On Linux, it is:
stable-x86_64-unknown-linux-gnu (default) rustc 1.48.0 (7eac88abb 2020-11-16)

[ivmarkov]

More on the "vendor" topic. If you want to use regular cargo instead of xargo:

1. Uncomment the "unstable" lines in .cargo/config in the repo of this demo app
2. Apply the workaround to your rust clone of my repo, as described here, at the bottom of the issue description.

[AdityaHPatwardhan]

@ivmarkov Thanks for the fix, I was able to build the rust side as well as the rust-esp32-std-hello example successfully. I was able to build that with cargo as well after applying your workaround.

[lucifer8851]

Thank you @ivmarkov for providing the solution. It has fixed the issue for me.
Closing down the issue.