Add support for aarch64 musl (#569)

Closes #87 

Does not include the `+static` variant as I was having a hard time
getting the bzip2 build passing. I'll open a new issue to track that.

Related #484

Author: zanieb

ci-targets.yaml

@@ -348,6 +348,26 @@ linux:
         minimum-python-version: "3.13"
     run: true
 
+  aarch64-unknown-linux-musl:
+    arch: aarch64
+    libc: musl
+    python_versions:
+      - "3.9"
+      - "3.10"
+      - "3.11"
+      - "3.12"
+      - "3.13"
+      - "3.14"
+    build_options:
+      # TODO: Static support is current blocked by some compiler-rt linking issues
+      # - debug+static
+      # - noopt+static
+      # - lto+static
+      - debug
+      - noopt
+      - lto
+    run: true
+
 windows:
   i686-pc-windows-msvc:
     arch: x86

cpython-unix/build-cpython-host.sh

@@ -70,6 +70,11 @@ case "${BUILD_TRIPLE}" in
     EXTRA_HOST_CPPFLAGS="${EXTRA_HOST_CPPFLAGS} -I/usr/include/x86_64-linux-gnu"
     EXTRA_HOST_LDFLAGS="${EXTRA_HOST_LDFLAGS} -L/usr/lib/x86_64-linux-gnu"
     ;;
+  aarch64-unknown-linux-gnu)
+    EXTRA_HOST_CFLAGS="${EXTRA_HOST_CFLAGS} -I/usr/include/aarch64-linux-gnu"
+    EXTRA_HOST_CPPFLAGS="${EXTRA_HOST_CPPFLAGS} -I/usr/include/aarch64-linux-gnu"
+    EXTRA_HOST_LDFLAGS="${EXTRA_HOST_LDFLAGS} -L/usr/lib/aarch64-linux-gnu"
+    ;;
   *)
     ;;
 esac

cpython-unix/build-cpython.sh

@@ -1077,8 +1077,14 @@ touch "${LIB_DYNLOAD}/.empty"
 
 # Symlink libpython so we don't have 2 copies.
 case "${TARGET_TRIPLE}" in
-aarch64-unknown-linux-gnu)
-    PYTHON_ARCH="aarch64-linux-gnu"
+aarch64-unknown-linux-*)
+    # In Python 3.13+, the musl target is identified in cross compiles and the output directory
+    # is named accordingly.
+    if [[ "${CC}" = "musl-clang" && -n "${PYTHON_MEETS_MINIMUM_VERSION_3_13}" ]]; then
+        PYTHON_ARCH="aarch64-linux-musl"
+    else
+        PYTHON_ARCH="aarch64-linux-gnu"
+    fi
     ;;
 # This is too aggressive. But we don't have patches in place for
 # setting the platform name properly on non-Darwin.

cpython-unix/build-zstd.sh

@@ -15,16 +15,20 @@ tar -xf zstd-${ZSTD_VERSION}.tar.gz
 pushd cpython-source-deps-zstd-${ZSTD_VERSION}/lib
 
 if [ "${CC}" = "musl-clang" ]; then
-    # In order to build the library with SSE2, BMI, and AVX2 intrinstics, we need musl-clang to find
+    # In order to build the library with intrinsics, we need musl-clang to find
     # headers that provide access to the intrinsics, as they are not provided by musl. These are
     # part of the include files that are part of clang. But musl-clang eliminates them from the
     # default include path. So copy them into place.
-    for h in ${TOOLS_PATH}/${TOOLCHAIN}/lib/clang/*/include/*intrin.h ${TOOLS_PATH}/${TOOLCHAIN}/lib/clang/*/include/{__wmmintrin_aes.h,__wmmintrin_pclmul.h,emmintrin.h,immintrin.h,mm_malloc.h}; do
+    for h in ${TOOLS_PATH}/${TOOLCHAIN}/lib/clang/*/include/*intrin.h ${TOOLS_PATH}/${TOOLCHAIN}/lib/clang/*/include/{__wmmintrin_aes.h,__wmmintrin_pclmul.h,emmintrin.h,immintrin.h,mm_malloc.h,arm_neon.h,arm_neon_sve_bridge.h,arm_bf16.h,arm_fp16.h,arm_acle.h,arm_vector_types.h}; do
         filename=$(basename "$h")
-        if [ -e "${TOOLS_PATH}/host/include/${filename}" ]; then
-            echo "warning: ${filename} already exists"
+        if [ -f "$h" ]; then
+            if [ -e "${TOOLS_PATH}/host/include/${filename}" ]; then
+                echo "warning: ${filename} already exists"
+            fi
+            cp "$h" ${TOOLS_PATH}/host/include/
+        else
+            echo "warning: ${filename} not found (skipping)"
         fi
-        cp "$h" ${TOOLS_PATH}/host/include/
     done
     EXTRA_TARGET_CFLAGS="${EXTRA_TARGET_CFLAGS} -I${TOOLS_PATH}/host/include/"
 
@@ -33,7 +37,7 @@ if [ "${CC}" = "musl-clang" ]; then
     # `qsort_r` is actually available so we patch it to include a check for glibc.
     patch -p1 <<EOF
 diff --git a/dictBuilder/cover.c b/dictBuilder/cover.c
-index 5e6e8bc..6ca72a1 100644
+index 2ef33c7..078e2ee 100644
 --- a/dictBuilder/cover.c
 +++ b/dictBuilder/cover.c
 @@ -241,7 +241,7 @@ typedef struct {
@@ -45,6 +49,24 @@ index 5e6e8bc..6ca72a1 100644
  /* C90 only offers qsort() that needs a global context. */
  static COVER_ctx_t *g_coverCtx = NULL;
  #endif
+@@ -290,7 +290,7 @@ static int COVER_cmp8(COVER_ctx_t *ctx, const void *lp, const void *rp) {
+  */
+ #if (defined(_WIN32) && defined(_MSC_VER)) || defined(__APPLE__)
+ static int WIN_CDECL COVER_strict_cmp(void* g_coverCtx, const void* lp, const void* rp) {
+-#elif defined(_GNU_SOURCE)
++#elif defined(_GNU_SOURCE) && defined(__GLIBC__)
+ static int COVER_strict_cmp(const void *lp, const void *rp, void *g_coverCtx) {
+ #else /* C90 fallback.*/
+ static int COVER_strict_cmp(const void *lp, const void *rp) {
+@@ -306,7 +306,7 @@ static int COVER_strict_cmp(const void *lp, const void *rp) {
+  */
+ #if (defined(_WIN32) && defined(_MSC_VER)) || defined(__APPLE__)
+ static int WIN_CDECL COVER_strict_cmp8(void* g_coverCtx, const void* lp, const void* rp) {
+-#elif defined(_GNU_SOURCE)
++#elif defined(_GNU_SOURCE) && defined(__GLIBC__)
+ static int COVER_strict_cmp8(const void *lp, const void *rp, void *g_coverCtx) {
+ #else /* C90 fallback.*/
+ static int COVER_strict_cmp8(const void *lp, const void *rp) {
 @@ -328,7 +328,7 @@ static void stableSort(COVER_ctx_t *ctx) {
      qsort_r(ctx->suffix, ctx->suffixSize, sizeof(U32),
              ctx,

cpython-unix/build.py

@@ -88,6 +88,11 @@ def add_target_env(env, build_platform, target_triple, build_env):
     extra_host_cflags = []
     extra_host_ldflags = []
 
+    # Add compiler-rt for aarch64-musl to resolve missing builtins
+    if target_triple == "aarch64-unknown-linux-musl":
+        extra_target_cflags.append("--rtlib=compiler-rt")
+        extra_target_ldflags.append("--rtlib=compiler-rt")
+
     if build_platform.startswith("linux_"):
         machine = platform.machine()
 

cpython-unix/targets.yml

@@ -1131,3 +1131,50 @@ x86_64_v4-unknown-linux-musl:
     - zlib
     - zstd
   openssl_target: linux-x86_64
+
+aarch64-unknown-linux-musl:
+  host_platforms:
+    - linux_x86_64
+    - linux_aarch64
+  pythons_supported:
+    - '3.9'
+    - '3.10'
+    - '3.11'
+    - '3.12'
+    - '3.13'
+    - '3.14'
+  needs_toolchain: true
+  docker_image_suffix: .debian9
+  needs_toolchain: true
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: musl-clang
+  target_cxx: clang++
+  target_cflags:
+    - '-fvisibility=hidden'
+  needs:
+    - autoconf
+    - bdb
+    - binutils
+    - bzip2
+    - expat
+    - libedit
+    - libffi-3.3
+    - libX11
+    - libXau
+    - libxcb
+    - m4
+    - mpdecimal
+    - musl
+    - ncurses
+    - openssl-3.0
+    - patchelf
+    - sqlite
+    - tcl
+    - tk
+    - uuid
+    - xorgproto
+    - xz
+    - zlib
+    - zstd
+  openssl_target: linux-aarch64

src/release.rs

@@ -339,6 +339,18 @@ pub static RELEASE_TRIPLES: Lazy<BTreeMap<&'static str, TripleRelease>> = Lazy::
             }],
         },
     );
+    h.insert(
+        "aarch64-unknown-linux-musl",
+        TripleRelease {
+            suffixes: vec!["debug", "lto", "noopt"],
+            install_only_suffix: "lto",
+            python_version_requirement: None,
+            conditional_suffixes: vec![ConditionalSuffixes {
+                python_version_requirement: VersionSpecifier::from_str(">=3.13").unwrap(),
+                suffixes: linux_suffixes_musl_freethreaded.clone(),
+            }],
+        },
+    );
 
     h
 });

src/validation.rs

@@ -35,6 +35,7 @@ const RECOGNIZED_TRIPLES: &[&str] = &[
     "aarch64-apple-ios",
     "aarch64-pc-windows-msvc",
     "aarch64-unknown-linux-gnu",
+    "aarch64-unknown-linux-musl",
     "armv7-unknown-linux-gnueabi",
     "armv7-unknown-linux-gnueabihf",
     "arm64-apple-tvos",
@@ -211,6 +212,10 @@ static GLIBC_MAX_VERSION_BY_TRIPLE: Lazy<HashMap<&'static str, version_compare::
         );
 
         // musl shouldn't link against glibc.
+        versions.insert(
+            "aarch64-unknown-linux-musl",
+            version_compare::Version::from("1").unwrap(),
+        );
         versions.insert(
             "x86_64-unknown-linux-musl",
             version_compare::Version::from("1").unwrap(),
@@ -549,6 +554,7 @@ static PLATFORM_TAG_BY_TRIPLE: Lazy<HashMap<&'static str, &'static str>> = Lazy:
         ("aarch64-apple-ios", "iOS-aarch64"),
         ("aarch64-pc-windows-msvc", "win-arm64"),
         ("aarch64-unknown-linux-gnu", "linux-aarch64"),
+        ("aarch64-unknown-linux-musl", "linux-aarch64"),
         ("armv7-unknown-linux-gnueabi", "linux-arm"),
         ("armv7-unknown-linux-gnueabihf", "linux-arm"),
         ("i686-pc-windows-msvc", "win32"),
@@ -949,6 +955,7 @@ fn validate_elf<Elf: FileHeader<Endian = Endianness>>(
 
     let wanted_cpu_type = match target_triple {
         "aarch64-unknown-linux-gnu" => object::elf::EM_AARCH64,
+        "aarch64-unknown-linux-musl" => object::elf::EM_AARCH64,
         "armv7-unknown-linux-gnueabi" => object::elf::EM_ARM,
         "armv7-unknown-linux-gnueabihf" => object::elf::EM_ARM,
         "i686-unknown-linux-gnu" => object::elf::EM_386,