Custom build command failing on aarch64

[slackers123]

After just crating a new Rust project and importing the mozangle dependency I get the following build error:

Updating crates.io index
... crates
   Compiling mozangle v0.5.3
warning: mozangle@0.5.3: clang++: warning: treating 'c' input as 'c++' when in C++ mode, this behavior is deprecated [-Wdeprecated]
error: failed to run custom build command for `mozangle v0.5.3`

Caused by:
  process didn't exit successfully: `/Users/severingebesmair/rust/angle_test/target/debug/build/mozangle-63ea97bac514622e/build-script-build` (exit status: 101)
  --- stdout
... cargo spam
  --- stderr
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/__config:1140:8: error: "No thread API"
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:1037:2: error: Unsupported architecture
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/machine/_types.h:36:2: error: architecture not supported
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:67:9: error: unknown type name '__int64_t'
... more types
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types.h:88:9: error: unknown type name '__uint32_t'
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/_types/_intptr_t.h:32:9: error: unknown type name '__darwin_intptr_t'
  /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/__availability:315:4: error: "It looks like you're trying to enable vendor availability markup, but you haven't defined the corresponding macros yet!"
  fatal error: too many errors emitted, stopping now [-ferror-limit=]

  thread 'main' panicked at /Users/severingebesmair/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/bindgen-0.71.1/lib.rs:890:13:
  assertion `left == right` failed: "arm64-apple-darwin" "aarch64-apple-darwin"
    left: 4
   right: 8
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

full output: https://pastebin.com/TwJMnFfB

This error first occurred after following the servo setup guide so I think I should have the environment set up correctly.

System:

CPU: Apple M3
OS: MacOS Sequoia 15.1
Model: MacBook Air

[jdm]

Can you try patching your bindgen dependency with the latest git version from https://github.com/rust-lang/rust-bindgen ? The assertion failure looks suspicious.

[jdm]

Can you figure out what version of clang you're using? I wonder if Servo's build is still on an xcode version with clang 16?

[slackers123]

After patching with [patch.crates-io] bindgen = { git = 'https://github.com/rust-lang/rust-bindgen.git' } (I am not familiar with patching I hope this is what you meant) and diffing I see no substantial differences.

Result of clang --version:

Apple clang version 16.0.0 (clang-1600.0.26.6)
Target: arm64-apple-darwin24.1.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

Is there some way of making sure that servo/mozangle is actually using this version of clang?

[jdm]

https://github.com/rust-lang/rust-bindgen/blob/35e7078e1c6dffc3ed11c5d8a1ae16f139118686/bindgen/lib.rs#L889-L894 is the assertion which is failing. It seems like somehow your libclang is trying to compile for a 32 bit target or something? That's super weird.

[jdm]

What build command are you running, and what does rustup show output?

[slackers123]

When trying to build servo I just run ./mach build -d and with the simple test project I just use cargo b.

Output of rustup show:

Default host: aarch64-apple-darwin
rustup home:  /Users/severingebesmair/.rustup

installed toolchains
--------------------

stable-aarch64-apple-darwin (default)
nightly-aarch64-apple-darwin
1.83.0-aarch64-apple-darwin
1.85.0-aarch64-apple-darwin
esp

installed targets for active toolchain
--------------------------------------

aarch64-apple-darwin
wasm32-unknown-unknown

active toolchain
----------------

stable-aarch64-apple-darwin (default)
rustc 1.85.0 (4d91de4e4 2025-02-17)

Also looking through some of the c/c++ errors it seems that clang doesn't define the __APPLE__ and __arm64__ macros leading to type errors.

Trying to specify the clang version exactly with the CLANG_PATH=/usr/bin/clang(++) environment variable as suggested in the clang_sys crate also results in the same errors.

[LorenzoBloedow]

I had the same issue, turns out my .zshrc file was setting the LIBCLANG_PATH env var (to cross-compile for an embedded target I was working on). After I removed the offending line, it built without any issues. @slackers123 try checking that 🙂

[slackers123]

Just did a quick test and it seems to work without even changing anything. I have completely wiped my setup since writing this post in may so while we may never know @LorenzoBloedow you were probably right since I did do some embedded cross compiling stuff at the time.