[ci] Check (but don't test) avr-none target (#2448)

Closes #2400

gherrit-pr-id: I69f30d9256afe91a6cf7619bec2b37b57ce98880

Author: joshlf

.github/workflows/ci.yml

@@ -631,6 +631,45 @@ jobs:
       - name: Check big endian for aarch64_be-unknown-linux-gnu target
         run: ./cargo.sh +nightly build --target=aarch64_be-unknown-linux-gnu -Zbuild-std --features simd
 
+  # We can't use this as part of the build matrix because rustup doesn't support
+  # the `avr-none` target.
+  check_avr_artmega:
+    runs-on: ubuntu-latest
+    name: Build (zerocopy / nightly / --simd / avr-none)
+    steps:
+      - uses: actions/checkout@eef61447b9ff4aafe5dcd4e0bbf5d482be7e7871 # v4.2.1
+      - name: Configure environment variables
+        run: |
+          set -eo pipefail
+          ZC_TOOLCHAIN="$(./cargo.sh --version nightly)"
+          RUSTFLAGS="$RUSTFLAGS $ZC_NIGHTLY_RUSTFLAGS"
+          echo "RUSTFLAGS=$RUSTFLAGS" >> $GITHUB_ENV
+          echo "ZC_TOOLCHAIN=$ZC_TOOLCHAIN" >> $GITHUB_ENV
+      - name: Rust Cache
+        uses: Swatinem/rust-cache@23bce251a8cd2ffc3c1075eaa2367cf899916d84 # v2.7.3
+        with:
+          key: avr-none
+      - name: Install stable Rust for use in 'cargo.sh'
+        uses: dtolnay/rust-toolchain@00b49be78f40fba4e87296b2ead62868750bdd83 # stable
+        with:
+          toolchain: stable
+      - name: Install Rust with nightly toolchain (${{ env.ZC_TOOLCHAIN }})
+        uses: dtolnay/rust-toolchain@00b49be78f40fba4e87296b2ead62868750bdd83 # stable
+        with:
+            toolchain: ${{ env.ZC_TOOLCHAIN }}
+            components: clippy, rust-src
+      # NOTE: We cannot check tests because of a number of different issues (at
+      # the time of writing):
+      # - No `alloc::sync`
+      # - Values of type `[u8; 32768]` are too big
+      #
+      # To try for yourself, replace `-Zbuild-std=core` with `-Zbuild-std` and
+      # add `--tests`.
+      - name: Check avr-none target
+        run: RUSTFLAGS='-C target-cpu=atmega328p' ./cargo.sh +nightly check --target=avr-none -Zbuild-std=core --features simd,simd-nightly,float-nightly,derive
+      - name: Clippy check avr-none target
+        run: RUSTFLAGS='-C target-cpu=atmega328p' ./cargo.sh +nightly clippy --target=avr-none -Zbuild-std=core --features simd,simd-nightly,float-nightly,derive
+
   check_fmt:
     runs-on: ubuntu-latest
     name: Check Rust formatting
@@ -761,7 +800,7 @@ jobs:
       # https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks
       if: failure()
       runs-on: ubuntu-latest
-      needs: [build_test, kani,check_be_aarch64 , check_fmt, check_readme, check_versions, generate_cache, check-all-toolchains-tested, check-job-dependencies, run-git-hooks]
+      needs: [build_test, kani, check_be_aarch64, check_avr_artmega, check_fmt, check_readme, check_versions, generate_cache, check-all-toolchains-tested, check-job-dependencies, run-git-hooks]
       steps:
         - name: Mark the job as failed
           run: exit 1

src/util/macro_util.rs

@@ -25,6 +25,7 @@ use core::{
 // TODO(#29), TODO(https://github.com/rust-lang/rust/issues/69835): Remove this
 // `cfg` when `size_of_val_raw` is stabilized.
 #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]
+#[cfg(not(target_pointer_width = "16"))]
 use core::ptr;
 
 use crate::{
@@ -105,11 +106,13 @@ impl<T, U> MaxAlignsOf<T, U> {
 }
 
 #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]
+#[cfg(not(target_pointer_width = "16"))]
 const _64K: usize = 1 << 16;
 
 // TODO(#29), TODO(https://github.com/rust-lang/rust/issues/69835): Remove this
 // `cfg` when `size_of_val_raw` is stabilized.
 #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]
+#[cfg(not(target_pointer_width = "16"))]
 #[repr(C, align(65536))]
 struct Aligned64kAllocation([u8; _64K]);
 
@@ -122,6 +125,7 @@ struct Aligned64kAllocation([u8; _64K]);
 // TODO(#29), TODO(https://github.com/rust-lang/rust/issues/69835): Remove this
 // `cfg` when `size_of_val_raw` is stabilized.
 #[cfg(__ZEROCOPY_INTERNAL_USE_ONLY_NIGHTLY_FEATURES_IN_TESTS)]
+#[cfg(not(target_pointer_width = "16"))]
 pub const ALIGNED_64K_ALLOCATION: NonNull<[u8]> = {
     const REF: &Aligned64kAllocation = &Aligned64kAllocation([0; _64K]);
     let ptr: *const Aligned64kAllocation = REF;