fix: build precompiled headers after generated inputs

pylib/gyp/generator/make.py

@@ -1477,6 +1477,27 @@ def WriteSources(
                 self.WriteLn(f"{obj}: {gch}")
             self.WriteLn("# End precompiled header dependencies")
 
+            # A prefix header may include generated headers, so the .gch has to
+            # wait for the same generated inputs the objects wait for. The rules
+            # above give the objects these as order-only prerequisites; without
+            # the same rules here the .gch races code generation, and a clean
+            # build fails on a missing generated header.
+            gchs = sorted({gch for _, _, gch in pchdeps})
+            if deps:
+                self.WriteMakeRule(
+                    gchs,
+                    deps,
+                    comment="Make sure our dependencies are built before the pch.",
+                    order_only=True,
+                )
+            if extra_outputs:
+                self.WriteMakeRule(
+                    gchs,
+                    extra_outputs,
+                    comment="Make sure our actions/rules run before the pch.",
+                    order_only=True,
+                )
+
         if objs:
             extra_link_deps.append("$(OBJS)")
             self.WriteLn(

test/fixtures/pch_prefix.gyp

@@ -0,0 +1,23 @@
+{
+  'targets': [
+    {
+      'target_name': 'pch_prefix',
+      'type': 'executable',
+      'sources': [ 'pch.cc' ],
+      'xcode_settings': {
+        'GCC_PREFIX_HEADER': 'pch.h',
+        'GCC_PRECOMPILE_PREFIX_HEADER': 'YES',
+      },
+      # A prefix header is allowed to include generated headers, so the .gch has
+      # to wait for this target's actions the same way its objects do.
+      'actions': [
+        {
+          'action_name': 'make_header',
+          'inputs': [],
+          'outputs': [ '<(SHARED_INTERMEDIATE_DIR)/generated.h' ],
+          'action': [ 'touch', '<(SHARED_INTERMEDIATE_DIR)/generated.h' ],
+        },
+      ],
+    },
+  ]
+}

test/integration_test.py

@@ -13,6 +13,7 @@
 fixture_dir = os.path.join(os.path.dirname(__file__), "fixtures")
 gyp_file = os.path.join(fixture_dir, "integration.gyp")
 pch_gyp_file = os.path.join(fixture_dir, "pch.gyp")
+pch_prefix_gyp_file = os.path.join(fixture_dir, "pch_prefix.gyp")
 
 if sys.platform == "win32":
     sysname = sys.platform
@@ -80,6 +81,36 @@ def test_cmake(self) -> None:
         assert_file(self, "out/Default/CMakeLists.txt", "cmake/CMakeLists.txt")
 
 
+class TestGypMac(unittest.TestCase):
+    def setUp(self) -> None:
+        if sysname != "darwin":
+            self.skipTest("macOS-only test")
+        shutil.rmtree(os.path.join(fixture_dir, "out"), ignore_errors=True)
+
+    def test_make_prefix_header_waits_for_generated_inputs(self) -> None:
+        rc = gyp.main(
+            [
+                "-f",
+                "make",
+                "--depth",
+                fixture_dir,
+                "--generator-output",
+                "out",
+                pch_prefix_gyp_file,
+            ]
+        )
+        assert rc == 0
+
+        with open(os.path.join(fixture_dir, "out/pch_prefix.target.mk")) as in_file:
+            mk = in_file.read()
+
+        gch = "$(obj).target/$(TARGET)/pch-cc/pch.h.gch"
+        assert f"$(obj).target/$(TARGET)/pch.o: {gch}" in mk
+        # A prefix header may include generated headers, so the .gch must carry
+        # the same order-only prerequisites the objects carry.
+        self.assertRegex(mk, re.escape(f"{gch}: |") + r".*make_header")
+
+
 class TestGypWindows(unittest.TestCase):
     def setUp(self) -> None:
         if sys.platform != "win32":