Add support for building iOS wheels.

README.md

@@ -24,18 +24,18 @@ What does it do?
 
 While cibuildwheel itself requires a recent Python version to run (we support the last three releases), it can target the following versions to build wheels:
 
-|                | macOS Intel | macOS Apple Silicon | Windows 64bit | Windows 32bit | Windows Arm64 | manylinux<br/>musllinux x86_64 | manylinux<br/>musllinux i686 | manylinux<br/>musllinux aarch64 | manylinux<br/>musllinux ppc64le | manylinux<br/>musllinux s390x | manylinux<br/>musllinux armv7l | Pyodide |
-|----------------|----|-----|-----|-----|-----|----|-----|----|-----|-----|---|-----|
-| CPython 3.8    | ✅ | ✅  | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A |
-| CPython 3.9    | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅ | ✅ | ✅  | ✅  | ✅⁵ | N/A |
-| CPython 3.10   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A |
-| CPython 3.11   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A |
-| CPython 3.12   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵  | ✅⁴ |
-| CPython 3.13³  | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵  | N/A |
-| PyPy 3.8 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A |
-| PyPy 3.9 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A |
-| PyPy 3.10 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A |
-| PyPy 3.11 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A |
+|                | macOS Intel | macOS Apple Silicon | Windows 64bit | Windows 32bit | Windows Arm64 | manylinux<br/>musllinux x86_64 | manylinux<br/>musllinux i686 | manylinux<br/>musllinux aarch64 | manylinux<br/>musllinux ppc64le | manylinux<br/>musllinux s390x | manylinux<br/>musllinux armv7l | iOS | Pyodide |
+|----------------|----|-----|-----|-----|-----|----|-----|----|-----|-----|---|-----|-----|
+| CPython 3.8    | ✅ | ✅  | ✅  | ✅  | N/A | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A | N/A |
+| CPython 3.9    | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅ | ✅ | ✅  | ✅  | ✅⁵ | N/A | N/A |
+| CPython 3.10   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A | N/A |
+| CPython 3.11   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵ | N/A | N/A |
+| CPython 3.12   | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵  | N/A | ✅⁴ |
+| CPython 3.13³  | ✅ | ✅  | ✅  | ✅  | ✅² | ✅ | ✅  | ✅ | ✅  | ✅  | ✅⁵  | ✅ | N/A |
+| PyPy 3.8 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A | N/A |
+| PyPy 3.9 v7.3  | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A | N/A |
+| PyPy 3.10 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A | N/A |
+| PyPy 3.11 v7.3 | ✅ | ✅  | ✅  | N/A | N/A | ✅¹ | ✅¹  | ✅¹ | N/A | N/A | N/A | N/A | N/A |
 
 <sup>¹ PyPy is only supported for manylinux wheels.</sup><br>
 <sup>² Windows arm64 support is experimental.</sup><br>
@@ -55,18 +55,19 @@ Usage
 
 `cibuildwheel` runs inside a CI service. Supported platforms depend on which service you're using:
 
-|                 | Linux | macOS | Windows | Linux ARM | macOS ARM | Windows ARM |
-|-----------------|-------|-------|---------|-----------|-----------|-------------|
-| GitHub Actions  | ✅    | ✅    | ✅       | ✅        | ✅        | ✅²         |
-| Azure Pipelines | ✅    | ✅    | ✅       |           | ✅        | ✅²         |
-| Travis CI       | ✅    |       | ✅      | ✅        |           |             |
-| AppVeyor        | ✅    | ✅    | ✅      |           | ✅        | ✅²         |
-| CircleCI        | ✅    | ✅    |         | ✅        | ✅        |             |
-| Gitlab CI       | ✅    | ✅    | ✅      | ✅¹       | ✅        |             |
-| Cirrus CI       | ✅    | ✅    | ✅      | ✅        | ✅        |             |
+|                 | Linux | macOS | Windows | Linux ARM | macOS ARM | Windows ARM | iOS |
+|-----------------|-------|-------|---------|-----------|-----------|-------------|-----|
+| GitHub Actions  | ✅    | ✅    | ✅       | ✅        | ✅        | ✅²         | ✅³  |
+| Azure Pipelines | ✅    | ✅    | ✅       |           | ✅        | ✅²         |     |
+| Travis CI       | ✅    |       | ✅      | ✅        |           |             |     |
+| AppVeyor        | ✅    | ✅    | ✅      |           | ✅        | ✅²         |     |
+| CircleCI        | ✅    | ✅    |         | ✅        | ✅        |             |     |
+| Gitlab CI       | ✅    | ✅    | ✅      | ✅¹       | ✅        |             |     |
+| Cirrus CI       | ✅    | ✅    | ✅      | ✅        | ✅        |             |     |
 
 <sup>¹ [Requires emulation](https://cibuildwheel.pypa.io/en/stable/faq/#emulation), distributed separately. Other services may also support Linux ARM through emulation or third-party build hosts, but these are not tested in our CI.</sup><br>
-<sup>² [Uses cross-compilation](https://cibuildwheel.pypa.io/en/stable/faq/#windows-arm64). It is not possible to test `arm64` on this CI platform.</sup>
+<sup>² [Uses cross-compilation](https://cibuildwheel.pypa.io/en/stable/faq/#windows-arm64). It is not possible to test `arm64` on this CI platform.</sup><br>
+<sup>³ Requires a macOS runner; runs tests on the simulator for the runner's architecture.</sup>
 
 <!--intro-end-->
 
@@ -75,6 +76,7 @@ Example setup
 
 To build manylinux, musllinux, macOS, and Windows wheels on GitHub Actions, you could use this `.github/workflows/wheels.yml`:
 
+<!--generic-github-start-->
 ```yaml
 name: Build
 
@@ -102,12 +104,14 @@ jobs:
         # to supply options, put them in 'env', like:
         # env:
         #   CIBW_SOME_OPTION: value
+        #   ...
 
       - uses: actions/upload-artifact@v4
         with:
           name: cibw-wheels-${{ matrix.os }}-${{ strategy.job-index }}
           path: ./wheelhouse/*.whl
 ```
+<!--generic-github-end-->
 
 For more information, including PyPI deployment, and the use of other CI services or the dedicated GitHub Action, check out the [documentation](https://cibuildwheel.pypa.io) and the [examples](https://github.com/pypa/cibuildwheel/tree/main/examples).
 

bin/generate_schema.py

@@ -305,6 +305,7 @@ def as_object(d: dict[str, Any]) -> dict[str, Any]:
     "windows": as_object(not_linux),
     "macos": as_object(not_linux),
     "pyodide": as_object(not_linux),
+    "ios": as_object(not_linux),
 }
 
 oses["linux"]["properties"]["repair-wheel-command"] = {

bin/run_tests.py

@@ -41,12 +41,15 @@
         sys.executable,
         "-m",
         "pytest",
+        "--dist",
+        "loadgroup",
         f"--numprocesses={args.num_processes}",
         "-x",
         "--durations",
         "0",
         "--timeout=2400",
         "test",
+        "-vv",
     ]
 
     if sys.platform.startswith("linux") and args.run_podman:

cibuildwheel/__main__.py

@@ -15,6 +15,7 @@
 from typing import Any, Protocol, TextIO, assert_never
 
 import cibuildwheel
+import cibuildwheel.ios
 import cibuildwheel.linux
 import cibuildwheel.macos
 import cibuildwheel.pyodide
@@ -93,13 +94,14 @@ def main_inner(global_options: GlobalOptions) -> None:
 
     parser.add_argument(
         "--platform",
-        choices=["auto", "linux", "macos", "windows", "pyodide"],
+        choices=["auto", "linux", "macos", "windows", "pyodide", "ios"],
         default=None,
         help="""
-            Platform to build for. Use this option to override the
-            auto-detected platform. Specifying "macos" or "windows" only works
-            on that operating system, but "linux" works on all three, as long
-            as Docker/Podman is installed. Default: auto.
+            Platform to build for. Use this option to override the auto-detected
+            platform. Specifying "macos" or "windows" only works on that
+            operating system. "linux" works on any desktop OS, as long as
+            Docker/Podman is installed. "pyodide" only works on linux and macOS.
+            "ios" only work on macOS. Default: auto.
         """,
     )
 
@@ -240,6 +242,8 @@ def _compute_platform_only(only: str) -> PlatformName:
         return "windows"
     if "pyodide_" in only:
         return "pyodide"
+    if "ios_" in only:
+        return "ios"
     msg = f"Invalid --only='{only}', must be a build selector with a known platform"
     raise errors.ConfigurationError(msg)
 
@@ -301,6 +305,8 @@ def get_platform_module(platform: PlatformName) -> PlatformModule:
         return cibuildwheel.macos
     if platform == "pyodide":
         return cibuildwheel.pyodide
+    if platform == "ios":
+        return cibuildwheel.ios
     assert_never(platform)
 
 

cibuildwheel/architecture.py

@@ -17,6 +17,7 @@
     "macos": "macOS",
     "windows": "Windows",
     "pyodide": "Pyodide",
+    "ios": "iOS",
 }
 
 ARCH_SYNONYMS: Final[list[dict[PlatformName, str | None]]] = [
@@ -63,6 +64,12 @@ class Architecture(StrEnum):
     # WebAssembly
     wasm32 = auto()
 
+    # iOS "multiarch" architectures that include both
+    # the CPU architecture and the ABI.
+    arm64_iphoneos = auto()
+    arm64_iphonesimulator = auto()
+    x86_64_iphonesimulator = auto()
+
     @staticmethod
     def parse_config(config: str, platform: PlatformName) -> "set[Architecture]":
         result = set()
@@ -89,8 +96,8 @@ def parse_config(config: str, platform: PlatformName) -> "set[Architecture]":
 
     @staticmethod
     def native_arch(platform: PlatformName) -> "Architecture | None":
-        if platform == "pyodide":
-            return Architecture.wasm32
+        native_machine = platform_module.machine()
+        native_architecture = Architecture(native_machine)
 
         # Cross-platform support. Used for --print-build-identifiers or docker builds.
         host_platform: PlatformName = (
@@ -99,8 +106,18 @@ def native_arch(platform: PlatformName) -> "Architecture | None":
             else ("macos" if sys.platform.startswith("darwin") else "linux")
         )
 
-        native_machine = platform_module.machine()
-        native_architecture = Architecture(native_machine)
+        if platform == "pyodide":
+            return Architecture.wasm32
+        elif platform == "ios":
+            # Can only build for iOS on macOS. The "native" architecture is the
+            # simulator for the macOS native platform.
+            if host_platform == "macos":
+                if native_architecture == Architecture.x86_64:
+                    return Architecture.x86_64_iphonesimulator
+                else:
+                    return Architecture.arm64_iphonesimulator
+            else:
+                return None
 
         # we might need to rename the native arch to the machine we're running
         # on, as the same arch can have different names on different platforms
@@ -131,9 +148,22 @@ def auto_archs(platform: PlatformName) -> "set[Architecture]":
             elif Architecture.aarch64 in result and _check_aarch32_el0():
                 result.add(Architecture.armv7l)
 
-        if platform == "windows" and Architecture.AMD64 in result:
+        elif platform == "windows" and Architecture.AMD64 in result:
             result.add(Architecture.x86)
 
+        elif platform == "ios":
+            # iOS defaults to building all targets with the same CPU architecture
+            # as the native simulator architecture
+            if native_arch == Architecture.x86_64_iphonesimulator:
+                result = {
+                    Architecture.x86_64_iphonesimulator,
+                }
+            else:
+                result = {
+                    Architecture.arm64_iphonesimulator,
+                    Architecture.arm64_iphoneos,
+                }
+
         return result
 
     @staticmethod
@@ -150,6 +180,11 @@ def all_archs(platform: PlatformName) -> "set[Architecture]":
             "macos": {Architecture.x86_64, Architecture.arm64, Architecture.universal2},
             "windows": {Architecture.x86, Architecture.AMD64, Architecture.ARM64},
             "pyodide": {Architecture.wasm32},
+            "ios": {
+                Architecture.x86_64_iphonesimulator,
+                Architecture.arm64_iphonesimulator,
+                Architecture.arm64_iphoneos,
+            },
         }
         return all_archs_map[platform]