Fixed the 32-bit Windows Python wheels by statically linking libgcc.

After some debugging I was able to determine that the Win32 DLL was failing to load libgcc_s_sjlj-1.dll.  If we statically link libgcc instead, there should be no runtime dependency on libgcc.

PiperOrigin-RevId: 448338965

.github/workflows/python_tests.yml

@@ -55,11 +55,10 @@ jobs:
           - { os: macos-12, python-version: "3.10", architecture: x64 }
           # Windows uses the full API up until Python 3.10, so each of these
           # jobs tests a distinct binary wheel.
-          # TODO(b/231485326): fix the win32 wheels to load properly.
-          # - { os: windows-2019, python-version: "3.7", architecture: x86 }
-          # - { os: windows-2019, python-version: "3.8", architecture: x86 }
-          # - { os: windows-2019, python-version: "3.9", architecture: x86 }
-          # - { os: windows-2019, python-version: "3.10", architecture: x86 }
+          - { os: windows-2019, python-version: "3.7", architecture: x86 }
+          - { os: windows-2019, python-version: "3.8", architecture: x86 }
+          - { os: windows-2019, python-version: "3.9", architecture: x86 }
+          - { os: windows-2019, python-version: "3.10", architecture: x86 }
           - { os: windows-2019, python-version: "3.7", architecture: x64 }
           - { os: windows-2019, python-version: "3.8", architecture: x64 }
           - { os: windows-2019, python-version: "3.9", architecture: x64 }
@@ -92,7 +91,7 @@ jobs:
       - name: Install Protobuf Wheels
         run: pip install -vvv --no-index --find-links wheels protobuf protobuftests
       - name: Test that module is importable
-        run: python -c 'from google._upb import _message; assert "google._upb._message.MessageMeta" in str(_message.MessageMeta)'
+        run: python -v -c 'from google._upb import _message; assert "google._upb._message.MessageMeta" in str(_message.MessageMeta)'
         if: ${{ !matrix.pure_python }}
       - name: Run the unit tests
         run: |

python/dist/BUILD.bazel

@@ -165,7 +165,7 @@ py_dist(
     binary_wheel = ":binary_wheel",
     full_api_cpus = [
         # TODO(b/231485326): fix win32 build
-        # "win32",
+        "win32",
         "win64",
     ],
     # Windows needs version-specific wheels until 3.10.
@@ -182,7 +182,7 @@ py_dist(
     # details).
     limited_api_wheels = {
         # TODO(b/231485326): fix win32 build
-        # "win32": "310",
+        "win32": "310",
         "win64": "310",
         "linux-x86_64": "37",
         "linux-aarch_64": "37",

python/protobuf.c

@@ -131,10 +131,14 @@ PyUpb_WeakMap* PyUpb_WeakMap_New(void) {
 
 void PyUpb_WeakMap_Free(PyUpb_WeakMap* map) { upb_Arena_Free(map->arena); }
 
+// To give better entropy in the table key, we shift away low bits that are
+// always zero.
+static const int PyUpb_PtrShift = (sizeof(void*) == 4) ? 2 : 3;
+
 uintptr_t PyUpb_WeakMap_GetKey(const void* key) {
   uintptr_t n = (uintptr_t)key;
-  assert((n & 7) == 0);
-  return n >> 3;
+  assert((n & ((1 << PyUpb_PtrShift) - 1)) == 0);
+  return n >> PyUpb_PtrShift;
 }
 
 void PyUpb_WeakMap_Add(PyUpb_WeakMap* map, const void* key, PyObject* py_obj) {
@@ -170,7 +174,7 @@ bool PyUpb_WeakMap_Next(PyUpb_WeakMap* map, const void** key, PyObject** obj,
   uintptr_t u_key;
   upb_value val;
   if (!upb_inttable_next2(&map->table, &u_key, &val, iter)) return false;
-  *key = (void*)(u_key << 3);
+  *key = (void*)(u_key << PyUpb_PtrShift);
   *obj = upb_value_getptr(val);
   return true;
 }

python/py_extension.bzl

@@ -17,7 +17,11 @@ def py_extension(name, srcs, copts, deps = []):
         srcs = srcs,
         copts = copts + ["-fvisibility=hidden"],
         linkopts = selects.with_or({
-            ("//python/dist:osx-x86_64_cpu", "//python/dist:osx-aarch64_cpu"): ["-undefined", "dynamic_lookup"],
+            (
+                "//python/dist:osx-x86_64_cpu",
+                "//python/dist:osx-aarch64_cpu",
+            ): ["-undefined", "dynamic_lookup"],
+            "//python/dist:win32_cpu": ["-static-libgcc"],
             "//conditions:default": [],
         }),
         linkshared = True,