unix: define the list of supported build targets in YAML config

Author: indygreg

cpython-unix/build-main.py

@@ -14,21 +14,20 @@
 from pythonbuild.utils import (
     compress_python_archive,
     release_tag_from_git,
+    supported_targets,
 )
 
 ROOT = pathlib.Path(os.path.abspath(__file__)).parent.parent
 BUILD = ROOT / "build"
 DIST = ROOT / "dist"
+SUPPORT = ROOT / "cpython-unix"
+TARGETS_CONFIG = SUPPORT / "targets.yml"
 
 
 def main():
     if sys.platform == "linux":
         host_platform = "linux64"
         default_target_triple = "x86_64-unknown-linux-gnu"
-        targets = {
-            "x86_64-unknown-linux-gnu",
-            "x86_64-unknown-linux-musl",
-        }
     elif sys.platform == "darwin":
         host_platform = "macos"
         machine = platform.machine()
@@ -39,17 +38,6 @@ def main():
             default_target_triple = "x86_64-apple-darwin"
         else:
             raise Exception("unhandled macOS machine value: %s" % machine)
-
-        targets = {
-            "aarch64-apple-darwin",
-            "aarch64-apple-ios",
-            "arm64-apple-tvos",
-            "thumbv7k-apple-watchos",
-            "x86_64-apple-darwin",
-            "x86_64-apple-ios",
-            "x86_64-apple-tvos",
-            "x86_64-apple-watchos",
-        }
     else:
         print("unsupport build platform: %s" % sys.platform)
         return 1
@@ -59,7 +47,7 @@ def main():
     parser.add_argument(
         "--target-triple",
         default=default_target_triple,
-        choices=targets,
+        choices=supported_targets(TARGETS_CONFIG),
         help="Target host triple to build for",
     )
 

cpython-unix/build.py

@@ -13,7 +13,6 @@
 import tempfile
 
 import docker
-import yaml
 
 from pythonbuild.buildenv import build_environment
 from pythonbuild.cpython import (
@@ -29,6 +28,7 @@
     add_env_common,
     add_licenses_to_extension_entry,
     download_entry,
+    get_targets,
     validate_python_json,
     write_package_versions,
     write_triples_makefiles,
@@ -53,12 +53,6 @@
 WATCHOS_DEPLOYMENT_TARGET = "7.0"
 
 
-def get_targets():
-    """Obtain the parsed targets YAML file."""
-    with TARGETS_CONFIG.open("rb") as fh:
-        return yaml.load(fh, Loader=yaml.SafeLoader)
-
-
 def install_sccache(build_env):
     """Attempt to install sccache into the build environment.
 
@@ -1080,7 +1074,7 @@ def main():
     with log_path.open("wb") as log_fh:
         set_logger(action, log_fh)
         if action == "makefiles":
-            write_triples_makefiles(get_targets(), BUILD)
+            write_triples_makefiles(get_targets(TARGETS_CONFIG), BUILD)
             write_package_versions(BUILD / "versions")
 
         elif action.startswith("image-"):

cpython-unix/targets.yml

@@ -1,5 +1,16 @@
+# This file defines configurations for each supported build target/triple.
+#
+# host_platform
+#    Defines the Python sys.platform value where this configuration
+#    can be built from.
+#
+# needs
+#    Packages required to build Python.
+
 ---
 aarch64-apple-darwin:
+  host_platforms:
+    - darwin
   needs:
     - libedit
     - libffi
@@ -9,18 +20,26 @@ aarch64-apple-darwin:
     - uuid
 
 aarch64-apple-ios:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 arm64-apple-tvos:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 thumb7k-apple-watchos:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 x86_64-apple-darwin:
+  host_platforms:
+    - darwin
   needs:
     - libedit
     - libffi
@@ -30,18 +49,26 @@ x86_64-apple-darwin:
     - uuid
 
 x86_64-apple-ios:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 x86_64-apple-tvos:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 x86_64-apple-watchos:
+  host_platforms:
+    - darwin
   needs:
     - sqlite
 
 x86_64-unknown-linux-gnu:
+  host_platforms:
+    - linux
   needs:
     - bdb
     - binutils
@@ -57,6 +84,8 @@ x86_64-unknown-linux-gnu:
     - uuid
 
 x86_64-unknown-linux-musl:
+  host_platforms:
+    - linux
   needs:
     - bdb
     - binutils

pythonbuild/utils.py

@@ -20,6 +20,24 @@
 from .logging import log
 
 
+def get_targets(yaml_path: pathlib.Path):
+    """Obtain the parsed targets YAML file."""
+    with yaml_path.open("rb") as fh:
+        return yaml.load(fh, Loader=yaml.SafeLoader)
+
+
+def supported_targets(yaml_path: pathlib.Path):
+    """Obtain a set of named targets that we can build."""
+    targets = set()
+
+    for target, settings in get_targets(yaml_path).items():
+        for platform in settings["host_platforms"]:
+            if sys.platform == platform:
+                targets.add(target)
+
+    return targets
+
+
 def release_tag_from_git():
     return (
         subprocess.check_output(