gh-135455: Fix version and architecture detection in PC/layout script. (GH-135461)

(cherry picked from commit afc5ab6cce)

Co-authored-by: Steve Dower <steve.dower@python.org>

PC/layout/support/constants.py

@@ -6,6 +6,8 @@
 __version__ = "3.8"
 
 import os
+import pathlib
+import re
 import struct
 import sys
 
@@ -13,9 +15,15 @@
 def _unpack_hexversion():
     try:
         hexversion = int(os.getenv("PYTHON_HEXVERSION"), 16)
+        return struct.pack(">i", hexversion)
     except (TypeError, ValueError):
-        hexversion = sys.hexversion
-    return struct.pack(">i", hexversion)
+        pass
+    if os.getenv("PYTHONINCLUDE"):
+        try:
+            return _read_patchlevel_version(pathlib.Path(os.getenv("PYTHONINCLUDE")))
+        except OSError:
+            pass
+    return struct.pack(">i", sys.hexversion)
 
 
 def _get_suffix(field4):
@@ -26,6 +34,39 @@ def _get_suffix(field4):
     return ""
 
 
+def _read_patchlevel_version(sources):
+    if not sources.match("Include"):
+        sources /= "Include"
+    values = {}
+    with open(sources / "patchlevel.h", "r", encoding="utf-8") as f:
+        for line in f:
+            m = re.match(r'#\s*define\s+(PY_\S+?)\s+(\S+)', line.strip(), re.I)
+            if m and m.group(2):
+                v = m.group(2)
+                if v.startswith('"'):
+                    v = v[1:-1]
+                else:
+                    v = values.get(v, v)
+                    if isinstance(v, str):
+                        try:
+                            v = int(v, 16 if v.startswith("0x") else 10)
+                        except ValueError:
+                            pass
+                values[m.group(1)] = v
+    return (
+        values["PY_MAJOR_VERSION"],
+        values["PY_MINOR_VERSION"],
+        values["PY_MICRO_VERSION"],
+        values["PY_RELEASE_LEVEL"] << 4 | values["PY_RELEASE_SERIAL"],
+    )
+
+
+def check_patchlevel_version(sources):
+    got = _read_patchlevel_version(sources)
+    if got != (VER_MAJOR, VER_MINOR, VER_MICRO, VER_FIELD4):
+        return f"{got[0]}.{got[1]}.{got[2]}{_get_suffix(got[3])}"
+
+
 VER_MAJOR, VER_MINOR, VER_MICRO, VER_FIELD4 = _unpack_hexversion()
 VER_SUFFIX = _get_suffix(VER_FIELD4)
 VER_FIELD3 = VER_MICRO << 8 | VER_FIELD4