Build failure when targeting `aarch64-pc-windows-gnullvm`

[rami3l]

Hi, it's me on behalf of the rustup team again!

Problem:

Some have asked for aarch64-pc-windows-gnullvm builds from rustup (rust-lang/rustup#3297), so this is the build failure from @magic-akari's first attempt in rust-lang/rustup#4523 when building rustup for that target:

+ cargo build --locked --profile dev --target aarch64-pc-windows-gnullvm --no-default-features --features curl-backend,reqwest-native-tls --features reqwest-rustls-tls
 Downloading crates ...
  Downloaded windows_aarch64_gnullvm v0.52.6
  Downloaded windows_aarch64_gnullvm v0.53.0
   Compiling proc-macro2 v1.0.101
   Compiling unicode-ident v1.0.19
   Compiling getrandom v0.3.3
   Compiling cfg-if v1.0.3
   Compiling find-msvc-tools v0.1.2
   Compiling shlex v1.3.0
   Compiling windows_aarch64_gnullvm v0.52.6
   Compiling pin-project-lite v0.2.16
   Compiling stable_deref_trait v1.2.0
   Compiling windows-targets v0.52.6
   Compiling pkg-config v0.3.32
   Compiling windows-sys v0.59.0
   Compiling jobserver v0.1.34
   Compiling quote v1.0.40
   Compiling syn v2.0.106
   Compiling cc v1.2.38
   Compiling windows-link v0.2.0
   Compiling bytes v1.10.1
   Compiling memchr v2.7.5
   Compiling once_cell v1.21.3
   Compiling libc v0.2.175
   Compiling futures-core v0.3.31
   Compiling windows-sys v0.61.0
   Compiling windows_aarch64_gnullvm v0.53.0
   Compiling itoa v1.0.15
   Compiling cmake v0.1.54
   Compiling synstructure v0.13.2
   Compiling socket2 v0.6.0
   Compiling mio v1.0.4
   Compiling fs_extra v1.3.0
   Compiling serde_core v1.0.226
   Compiling dunce v1.0.5
   Compiling windows-targets v0.53.3
   Compiling aws-lc-sys v0.31.0
   Compiling futures-sink v0.3.31
   Compiling smallvec v1.15.1
   Compiling windows-sys v0.60.2
   Compiling zerofrom-derive v0.1.6
   Compiling yoke-derive v0.8.0
   Compiling tokio-macros v2.5.0
   Compiling zerovec-derive v0.11.1
   Compiling zerofrom v0.1.6
   Compiling yoke v0.8.0
   Compiling displaydoc v0.2.5
   Compiling tokio v1.47.1
   Compiling zerovec v0.11.4
   Compiling fnv v1.0.7
   Compiling http v1.3.1
   Compiling tinystr v0.8.1
   Compiling tracing-core v0.1.34
   Compiling zerocopy v0.8.27
   Compiling writeable v0.6.1
   Compiling litemap v0.8.0
   Compiling aws-lc-rs v1.14.0
   Compiling slab v0.4.11
   Compiling icu_locale_core v2.0.0
   Compiling potential_utf v0.1.3
   Compiling zerotrie v0.2.2
   Compiling tracing-attributes v0.1.30
warning: aws-lc-sys@0.31.0: Building with: CMake
warning: aws-lc-sys@0.31.0: Symbol Prefix: Some("aws_lc_0_31_0")
warning: aws-lc-sys@0.31.0: Environment Variable found 'CMAKE': 'cmake'
warning: aws-lc-sys@0.31.0: CMAKE environment variable set: cmake
warning: aws-lc-sys@0.31.0: ######
warning: aws-lc-sys@0.31.0: If bindgen is unable to locate a header file, use the BINDGEN_EXTRA_CLANG_ARGS environment variable to specify additional include paths.
warning: aws-lc-sys@0.31.0: See: https://github.com/rust-lang/rust-bindgen?tab=readme-ov-file#environment-variables
warning: aws-lc-sys@0.31.0: ######
warning: aws-lc-sys@0.31.0: Generating bindings - external bindgen. Platform: aarch64-pc-windows-gnullvm
error: failed to run custom build command for `aws-lc-sys v0.31.0`

Caused by:
  process didn't exit successfully: `C:\a\rustup\rustup\target\debug\build\aws-lc-sys-f2ff7ca279845f11\build-script-main` (exit code: 101)
  --- stdout
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_PREFIX_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_PREFIX
  cargo:rerun-if-env-changed=AWS_LC_SYS_PREGENERATING_BINDINGS_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_PREGENERATING_BINDINGS
  cargo:rerun-if-env-changed=AWS_LC_SYS_EXTERNAL_BINDGEN_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_EXTERNAL_BINDGEN
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_ASM_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_ASM
  cargo:rerun-if-env-changed=AWS_LC_SYS_CFLAGS_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_CFLAGS
  cargo:rerun-if-env-changed=CFLAGS_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=CFLAGS
  cargo:rerun-if-env-changed=AWS_LC_SYS_PREBUILT_NASM_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_PREBUILT_NASM
  cargo:rerun-if-env-changed=AWS_LC_SYS_C_STD_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_C_STD
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE_BUILDER_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE_BUILDER
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_PREGENERATED_SRC_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_NO_PREGENERATED_SRC
  cargo:rerun-if-env-changed=AWS_LC_SYS_EFFECTIVE_TARGET_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_EFFECTIVE_TARGET
  cargo:rerun-if-env-changed=AWS_LC_SYS_STATIC_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_STATIC
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE
  cargo:rerun-if-env-changed=CMAKE_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=CMAKE
  cargo:warning=Building with: CMake
  cargo:warning=Symbol Prefix: Some("aws_lc_0_31_0")
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_CMAKE
  cargo:rerun-if-env-changed=CMAKE_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=CMAKE
  cargo:warning=Environment Variable found 'CMAKE': 'cmake'
  cargo:warning=CMAKE environment variable set: cmake
  cargo:warning=######
  cargo:warning=If bindgen is unable to locate a header file, use the BINDGEN_EXTRA_CLANG_ARGS environment variable to specify additional include paths.
  cargo:warning=See: https://github.com/rust-lang/rust-bindgen?tab=readme-ov-file#environment-variables
  cargo:warning=######
  cargo:warning=Generating bindings - external bindgen. Platform: aarch64-pc-windows-gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_INCLUDES_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_INCLUDES

  --- stderr
  Failure invoking external bindgen! 

  bindgen-PARAMS: --prefix-link-name aws_lc_0_31_0_ --allowlist-file .*(/|\\)openssl((/|\\)[^/\\]+)+\.h --allowlist-file .*(/|\\)rust_wrapper\.h --rustified-enum point_conversion_form_t --default-macro-constant-type signed --with-derive-default --with-derive-partialeq --with-derive-eq --raw-line 
  // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  // SPDX-License-Identifier: Apache-2.0 OR ISC
   --generate functions,types,vars,methods,constructors,destructors C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\include\rust_wrapper.h --rust-target 1.70 --output C:\a\rustup\rustup\target\aarch64-pc-windows-gnullvm\debug\build\aws-lc-sys-c960ff6c5b2cc9b4\out\bindings.rs --formatter rustfmt -- -I C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\include -I C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\aws-lc\include
  bindgen-STDOUT: 
  bindgen-STDERR: error: version 'llvm' in target triple 'aarch64-pc-windows-gnullvm' is invalid
  C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found
  Unable to generate bindings: clang diagnosed error: error: version 'llvm' in target triple 'aarch64-pc-windows-gnullvm' is invalid
  C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found



  thread 'main' panicked at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.31.0\builder\main.rs:758:5:
  aws-lc-sys build failed. Please enable the 'bindgen' feature on aws-lc-rs or aws-lc-sys.For more information, see the aws-lc-rs User Guide: https://aws.github.io/aws-lc-rs/index.html
  stack backtrace:
  note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
warning: build failed, waiting for other jobs to finish...
Error: Process completed with exit code 1.

However I'm not 100% sure if this is a problem on your side, since this time it's bindgen failing? Or it could be that we have to configure something on our side?

I did a GitHub Global Search and could only find xiph/rav1e#3393, not sure if that's completely related.

Relevant details

AWS-LC for Rust versions:

[[package]]
name = "aws-lc-rs"
version = "1.14.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "94b8ff6c09cd57b16da53641caa860168b88c172a5ee163b0288d3d6eea12786"
dependencies = [
 "aws-lc-sys",
 "zeroize",
]

[[package]]
name = "aws-lc-sys"
version = "0.31.0"
source = "registry+https://github.com/rust-lang/crates.io-index"
checksum = "0e44d16778acaf6a9ec9899b92cebd65580b83f685446bf2e1f5d3d732f99dcd"
dependencies = [
 "bindgen",
 "cc",
 "cmake",
 "dunce",
 "fs_extra",
]

System information:

Current runner version: '2.328.0'
Runner Image Provisioner
  Hosted Compute Agent
  Version: 20250912.392
  Commit: d921fda672a98b64f4f82364647e2f10b2267d0b
  Build Date: 2025-09-12T15:23:14Z
VM Image
  - OS: Windows (Arm64)
  - Source: Partner
  - Name: Microsoft Windows 11 Desktop by Arm Limited
  - Version: 20250930.30.1
  - Included Software: https://github.com/actions/partner-runner-images/blob/main/images/arm-windows-11-image.md

[justsmth]

Hello!

clang diagnosed error: error: version 'llvm' in target triple 'aarch64-pc-windows-gnullvm' is invalid

I believe this originates within the Clang library -- not-so-much bindgen -- as clang doesn't recognize gnullvm as a valid target ABI/environment. This might be fixed in more recent libclang versions? The error I'm seeing when attempting to build for this target is just related to it being unable to find "stddef.h"

  bindgen-STDERR: C:\Users\Administrator\repos\aws-lc-rs\aws-lc-sys\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found
  Unable to generate bindings: clang diagnosed error: C:\Users\Administrator\repos\aws-lc-rs\aws-lc-sys\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found

I have a possible workaround. You can use the AWS_LC_SYS_EFFECTIVE_TARGET environment variable (or its target-specific form) to have aws-lc-sys instead generate bindings for aarch64-pc-windows-gnu:

AWS_LC_SYS_EFFECTIVE_TARGET_aarch64_pc_windows_gnullvm=aarch64-pc-windows-gnu

(I believe the difference between *-gnu and *-gnullvm relates only to which C-runtime it's linked to.)

You might even "cheat" and have it use some pregenerated bindings to avoid needing bindgen:

AWS_LC_SYS_EFFECTIVE_TARGET_aarch64_pc_windows_gnullvm=x86_64-pc-windows-gnu

In the next few weeks, we plan to eliminate our bindgen requirement altogether with universal bindings. This will likely be part of a aws-lc-rs v1.15.0 release.

Please let us know if this workaround doesn't work for you. I can dig deeper to understand this failure. Thanks!

[rami3l]

@justsmth Thanks for the quick response! I'll get back to you once I've tried your suggestion on our CI.

[rami3l]

@justsmth I've tried that and unfortunately it didn't seem to work:

[..]
  cargo:warning=Generating bindings - external bindgen. Platform: aarch64-pc-windows-gnu
  cargo:rerun-if-env-changed=AWS_LC_SYS_INCLUDES_aarch64_pc_windows_gnullvm
  cargo:rerun-if-env-changed=AWS_LC_SYS_INCLUDES
  --- stderr
  Failure invoking external bindgen! 
  bindgen-PARAMS: --prefix-link-name aws_lc_0_32_2_ --allowlist-file .*(/|\\)openssl((/|\\)[^/\\]+)+\.h --allowlist-file .*(/|\\)rust_wrapper\.h --rustified-enum point_conversion_form_t --default-macro-constant-type signed --with-derive-default --with-derive-partialeq --with-derive-eq --raw-line 
  // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
  // SPDX-License-Identifier: Apache-2.0 OR ISC
   --generate functions,types,vars,methods,constructors,destructors C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\include\rust_wrapper.h --rust-target 1.70 --output C:\a\rustup\rustup\target\aarch64-pc-windows-gnullvm\release\build\aws-lc-sys-64d0eb53a52a74bb\out\bindings.rs --formatter rustfmt -- -I C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\include -I C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\aws-lc\include
  bindgen-STDOUT: 
  bindgen-STDERR: error: version 'llvm' in target triple 'aarch64-pc-windows-gnullvm' is invalid
  C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found
  Unable to generate bindings: clang diagnosed error: error: version 'llvm' in target triple 'aarch64-pc-windows-gnullvm' is invalid
  C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\aws-lc\include\openssl/base.h:59:10: fatal error: 'stddef.h' file not found
  thread 'main' panicked at C:\Users\runneradmin\.cargo\registry\src\index.crates.io-1949cf8c6b5b557f\aws-lc-sys-0.32.2\builder\main.rs:758:5:
  aws-lc-sys build failed. Please enable the 'bindgen' feature on aws-lc-rs or aws-lc-sys.For more information, see the aws-lc-rs User Guide: https://aws.github.io/aws-lc-rs/index.html
[..]

We are not in an absolute hurry, and the support for this target can even wait until later versions.

That said, I'm still curious about the new version you've mentioned. Will eliminate this requirement?

Many thanks in advance! 🙏

[justsmth]

I've tried that and unfortunately it didn't seem to work:

Ahh.. You're right. The AWS_LC_SYS_EFFECTIVE_TARGET doesn't affect the bindgen invocation, only the selection of bindings. (I'm experimenting with a way to address that here.)

That said, I'm still curious about the new version you've mentioned. Will eliminate this requirement?

Yes! The plan is to generate "universal" bindings. These pregenerated bindings will be available for all platforms, but limited more narrowly to the subset of the AWS-LC API that is used by aws-lc-rs. (The universal bindings will avoid providing definitions for libc structs like FILE that are potentially problematic for consumers.)