copyberry · Sep 5, 2026 · Sep 5, 2026
diff --git a/third_party/voice/BUILD.bazel b/third_party/voice/BUILD.bazel
@@ -46,6 +46,7 @@ filegroup(
         "package_runtime.py",
         "runtime.py",
         "sdk.py",
+        "windows_build_inputs.py",
         "windows_runtime.py",
         ":source_inputs",
     ],
@@ -56,6 +57,7 @@ filegroup(
     name = "native_recipe",
     srcs = [
         "build_native.py",
+        "windows_build_inputs.py",
         ":source_inputs",
     ],
 )

diff --git a/third_party/voice/README.md b/third_party/voice/README.md
@@ -114,6 +114,23 @@ Windows requires the normal Visual Studio SDK environment, Cygwin GNU make,
 bash/cygpath and Automake 1.18's standard `ar-lib` for upstream libffi,
 native Windows pkgconf, and `--bootstrap-make` pointing to NMake.
 The recipe does not install these build prerequisites or patch upstream sources.
+The optional `--windows-build-inputs <json>` argument records an explicit selection
+of these tools, the target-specific MSVC assembler, linker, library manager,
+inspector, Windows SDK resource/manifest tools, Python, and include/library roots.
+The existing private CI driver supplies this input from its provisioned VS/Cygwin
+setup. In this mode the recipe checks that named tools resolve to the selected
+files, puts MSVC ahead of Cygwin's different `link.exe`, and excludes unrelated
+inherited PATH and SDK entries. The exact selection is retained in build receipts.
+The JSON uses `schemaVersion: 1`, `target`, `tools` (role to absolute file path),
+`systemRoot`, and `INCLUDE`/`LIB` arrays of absolute directories. The CLI tool
+arguments must agree with the recorded selection. Without this argument, the
+standalone recipe keeps using the normal Visual Studio environment.
+
+This selects already installed inputs; it does not hash their support files,
+sandbox the build, supply a Bazel Windows provider, or publish build tools.
+Those still require a complete declared compiler/bootstrap closure and approved
+public-readable inputs. Existing private Cygwin release assets do not satisfy
+public self-build access. No Windows support is disabled to hide that gap.
 The private CI bootstrap verifies the official Cygwin installer and native pkgconf
 MSI hashes before use. It also verifies a retained Cygwin package snapshot against
 pinned archive and member hashes before installing it offline using signed

diff --git a/third_party/voice/build_native.py b/third_party/voice/build_native.py
@@ -16,6 +16,7 @@
 # without adding the caller's working directory to the module search path.
 sys.path.insert(0, str(Path(__file__).resolve().parent))
 from prepare_sources import MANIFEST, load_sources, prepare_sources
+from windows_build_inputs import build_environment
 
 TARGET_SYSTEMS = {
     "apple-darwin": "Darwin",
@@ -89,6 +90,21 @@ def __init__(self, args, inherited_environment):
         for tool in (*self.toolchain.values(), self.bootstrap_make):
             if not tool.is_file():
                 raise ValueError(f"Missing build tool: {tool}")
+        windows_inputs = getattr(args, "windows_build_inputs", None)
+        input_record = None
+        if windows_inputs is not None:
+            if not self.windows:
+                raise ValueError("Windows build inputs require a Windows MSVC target")
+            explicit, input_record = build_environment(
+                windows_inputs,
+                args.target,
+                {
+                    **self.toolchain,
+                    "bootstrap_make": self.bootstrap_make,
+                    "python": Path(sys.executable),
+                },
+            )
+            inherited_environment = {**inherited_environment, **explicit}
         if self.windows and not all(
             inherited_environment.get(key) for key in ("INCLUDE", "LIB")
         ):
@@ -117,9 +133,15 @@ def __init__(self, args, inherited_environment):
             )
             or (self.windows and key == "USERPROFILE")
         }
+        if windows_inputs is not None:
+            self.environment.pop("LIBPATH", None)
         paths = [
             str(self.tools / "bin"),
-            *(str(p.parent) for p in self.toolchain.values()),
+            *(
+                []
+                if windows_inputs is not None
+                else [str(p.parent) for p in self.toolchain.values()]
+            ),
         ]
         paths += (
             inherited_environment.get("PATH", "").split(os.pathsep)
@@ -172,6 +194,8 @@ def __init__(self, args, inherited_environment):
             "flags": self.flags,
             "steps": [],
         }
+        if input_record is not None:
+            self.record["windows_build_inputs"] = input_record
 
     def run(self, name, command, cwd=None, environment=None):
         command = [str(part) for part in command]
@@ -524,6 +548,11 @@ def main():
         type=Path,
         help="NMake on Windows; defaults to --make elsewhere",
     )
+    parser.add_argument(
+        "--windows-build-inputs",
+        type=Path,
+        help="Explicit Windows tool and SDK selection; no unrelated PATH fallback",
+    )
     for name in ("ar", "ranlib"):
         parser.add_argument(f"--{name}", type=Path)
     for name in ("c-flag", "cxx-flag", "link-flag"):

diff --git a/third_party/voice/test_build_native.py b/third_party/voice/test_build_native.py
@@ -535,3 +535,34 @@ def record(name, command, **kwargs):
                     result.stdout.strip(),
                     linker_flags,
                 )
+
+    def test_explicit_windows_inputs_replace_ambient_sdk_and_search_paths(self):
+        self.args.target = "x86_64-pc-windows-msvc"
+        self.args.windows_build_inputs = self.root / "inputs.json"
+        selected = {
+            "PATH": str(self.root / "selected tools"),
+            "INCLUDE": str(self.root / "selected include"),
+            "LIB": str(self.root / "selected lib"),
+        }
+        with (
+            patch("build_native.validate_target"),
+            patch(
+                "build_native.build_environment",
+                return_value=(selected, {"target": self.args.target}),
+            ),
+        ):
+            build = NativeBuild(
+                self.args,
+                {"PATH": "/unrelated", "LIBPATH": "/unrelated"},
+            )
+        self.assertFalse(
+            any("/unrelated" in value for value in build.environment.values())
+        )
+        self.assertEqual(
+            {name: build.environment[name] for name in ("INCLUDE", "LIB")},
+            {name: selected[name] for name in ("INCLUDE", "LIB")},
+        )
+        self.assertEqual(
+            build.record["windows_build_inputs"], {"target": self.args.target}
+        )
+        self.assertFalse(build.output.exists())
diff --git a/third_party/voice/test_windows_build_inputs.py b/third_party/voice/test_windows_build_inputs.py
@@ -0,0 +1,148 @@
+"""Exercise explicit Windows tool selection and rejection before native builds."""
+
+import json
+import os
+from pathlib import Path
+import shutil
+import subprocess
+import sys
+import tempfile
+import unittest
+
+from windows_build_inputs import build_environment
+
+
+class WindowsInputsTests(unittest.TestCase):
+    def setUp(self):
+        temporary = tempfile.TemporaryDirectory(prefix="voice selected tools ")
+        self.addCleanup(temporary.cleanup)
+        self.root = Path(temporary.name)
+        self.target = "x86_64-pc-windows-msvc"
+        self.selected = {}
+        for directory, names in {
+            "msvc": [
+                "cl.exe",
+                "link.exe",
+                "lib.exe",
+                "dumpbin.exe",
+                "ml64.exe",
+                "nmake.exe",
+            ],
+            "sdk": ["rc.exe", "mt.exe"],
+            "cygwin": [
+                "bash.exe",
+                "cygpath.exe",
+                "automake-1.18",
+                "make.exe",
+                "link.exe",
+            ],
+            "cmake": ["cmake.exe"],
+            "pkgconf": ["pkgconf.exe"],
+            "Windows/System32": ["cmd.exe"],
+        }.items():
+            parent = self.root / directory
+            parent.mkdir(parents=True)
+            for name in names:
+                (parent / name).touch()
+        self.tools = {
+            "cc": self.root / "msvc/cl.exe",
+            "cxx": self.root / "msvc/cl.exe",
+            "link": self.root / "msvc/link.exe",
+            "lib": self.root / "msvc/lib.exe",
+            "dumpbin": self.root / "msvc/dumpbin.exe",
+            "assembler": self.root / "msvc/ml64.exe",
+            "bootstrap_make": self.root / "msvc/nmake.exe",
+            "rc": self.root / "sdk/rc.exe",
+            "mt": self.root / "sdk/mt.exe",
+            "make": self.root / "cygwin/make.exe",
+            "shell": self.root / "cygwin/bash.exe",
+            "cygpath": self.root / "cygwin/cygpath.exe",
+            "automake": self.root / "cygwin/automake-1.18",
+            "cmake": self.root / "cmake/cmake.exe",
+            "pkg_config": self.root / "pkgconf/pkgconf.exe",
+            "python": Path(sys.executable),
+        }
+        self.document = {
+            "schemaVersion": 1,
+            "target": self.target,
+            "tools": {key: str(value) for key, value in self.tools.items()},
+            "systemRoot": str(self.root / "Windows"),
+            "INCLUDE": [str(self.root / "sdk")],
+            "LIB": [str(self.root / "msvc")],
+        }
+        self.path = self.root / "inputs.json"
+
+    def environment(self):
+        self.path.write_text(json.dumps(self.document), encoding="utf-8")
+        return build_environment(self.path, self.target, self.selected)[0]
+
+    def test_msvc_link_precedes_same_named_cygwin_tool(self):
+        environment = self.environment()
+        first = next(
+            Path(directory) / "link.exe"
+            for directory in environment["PATH"].split(os.pathsep)
+            if (Path(directory) / "link.exe").exists()
+        )
+        self.assertEqual(first, self.tools["link"])
+        self.assertEqual(
+            {name: environment[name] for name in ("INCLUDE", "LIB", "COMSPEC")},
+            {
+                "INCLUDE": str(self.root / "sdk"),
+                "LIB": str(self.root / "msvc"),
+                "COMSPEC": str(self.root / "Windows/System32/cmd.exe"),
+            },
+        )
+
+    @unittest.skipIf(os.name == "nt", "Portable shell subprocess selection probe")
+    def test_subprocess_uses_selected_tool_without_ambient_path(self):
+        # Execute the name upstream uses, with a conflicting Cygwin executable.
+        for path, text in (
+            (self.tools["link"], "msvc"),
+            (self.root / "cygwin/link.exe", "cygwin"),
+        ):
+            path.write_text(f"#!/bin/sh\nprintf '{text}'\n")
+            path.chmod(0o755)
+        result = subprocess.run(
+            ["link.exe"],
+            env=self.environment(),
+            check=True,
+            capture_output=True,
+            text=True,
+        )
+        self.assertEqual(result.stdout, "msvc")
+
+    def test_missing_or_wrong_architecture_assembler_is_rejected(self):
+        self.tools["assembler"].unlink()
+        with self.assertRaisesRegex(ValueError, "assembler"):
+            self.environment()
+        self.tools["assembler"].touch()
+        self.target = "aarch64-pc-windows-msvc"
+        self.document["target"] = self.target
+        with self.assertRaisesRegex(ValueError, "assembler"):
+            self.environment()
+        arm = self.tools["assembler"].with_name("armasm64.exe")
+        arm.touch()
+        self.document["tools"]["assembler"] = str(arm)
+        self.environment()
+
+    def test_shadowed_sdk_tool_is_rejected(self):
+        shutil.copyfile(self.tools["rc"], self.root / "msvc/rc.exe")
+        with self.assertRaisesRegex(ValueError, "shadowed: rc"):
+            self.environment()
+
+    def test_cli_tool_must_match_recorded_selection(self):
+        self.selected["cc"] = self.tools["cmake"]
+        with self.assertRaisesRegex(ValueError, "disagrees with --cc"):
+            self.environment()
+
+    def test_missing_sdk_and_relative_paths_are_rejected(self):
+        for value in ([], ["relative"], [str(self.root / "missing")]):
+            with self.subTest(value=value):
+                self.document["INCLUDE"] = value
+                with self.assertRaises(ValueError):
+                    self.environment()
+
+    def test_target_mismatch_cannot_reuse_other_inputs(self):
+        self.document["target"] = "aarch64-pc-windows-msvc"
+        with self.assertRaisesRegex(ValueError, "target"):
+            self.environment()
diff --git a/third_party/voice/windows_build_inputs.py b/third_party/voice/windows_build_inputs.py
@@ -0,0 +1,89 @@
+"""Select already provisioned Windows build tools without unrelated PATH entries.
+
+This is an input-selection contract, not a sandbox or a hashed tool closure.
+The selected tools still depend on their installed support files and Windows.
+"""
+
+import json
+import os
+from pathlib import Path
+
+
+def build_environment(path, target, selected_tools):
+    if path.stat().st_size > 65536:
+        raise ValueError("Windows build input document exceeds limits")
+    inputs = json.loads(path.read_text(encoding="utf-8"))
+    expected = {
+        "cc": "cl.exe",
+        "cxx": "cl.exe",
+        "link": "link.exe",
+        "lib": "lib.exe",
+        "dumpbin": "dumpbin.exe",
+        "assembler": "ml64.exe" if target.startswith("x86_64-") else "armasm64.exe",
+        "rc": "rc.exe",
+        "mt": "mt.exe",
+        "cmake": "cmake.exe",
+        "bootstrap_make": "nmake.exe",
+        "make": "make.exe",
+        "shell": "bash.exe",
+        "cygpath": "cygpath.exe",
+        "automake": "automake-1.18",
+    }
+    if (
+        target not in ("x86_64-pc-windows-msvc", "aarch64-pc-windows-msvc")
+        or inputs.get("schemaVersion") != 1
+        or inputs.get("target") != target
+        or set(inputs.get("tools", {})) != {*expected, "pkg_config", "python"}
+    ):
+        raise ValueError("Windows build inputs do not match the target and tool set")
+    tools = {}
+    for name, value in inputs["tools"].items():
+        tool = Path(value)
+        if (
+            not tool.is_absolute()
+            or not tool.is_file()
+            or ";" in str(tool)
+            or (name in expected and tool.name.lower() != expected[name])
+        ):
+            raise ValueError(f"Invalid Windows build tool: {name}")
+        tools[name] = tool
+    for name, tool in selected_tools.items():
+        if not tools[name].samefile(tool):
+            raise ValueError(f"Windows build input disagrees with --{name}")
+    # libffi invokes cl/link/lib and its architecture's assembler by name.
+    # Keep MSVC ahead of Cygwin, which also installs a different link.exe.
+    directories = list(dict.fromkeys(tools[name].parent for name in expected))
+    directories += [tools[name].parent for name in ("pkg_config", "python")]
+    directories = list(dict.fromkeys(directories))
+    for name, filename in expected.items():
+        found = next(
+            (p / filename for p in directories if (p / filename).is_file()), None
+        )
+        if found is None or not found.samefile(tools[name]):
+            raise ValueError(f"Windows build tool is shadowed: {name}")
+    system = Path(inputs["systemRoot"])
+    command = system / "System32/cmd.exe"
+    if not system.is_absolute() or not command.is_file() or ";" in str(system):
+        raise ValueError(
+            "Windows build inputs require a valid system command directory"
+        )
+    directories.append(command.parent)
+    environment = {
+        "PATH": os.pathsep.join(map(str, directories)),
+        "SystemRoot": str(system),
+        "SYSTEMROOT": str(system),
+        "WINDIR": str(system),
+        "COMSPEC": str(command),
+    }
+    for name in ("INCLUDE", "LIB"):
+        values = inputs.get(name)
+        if not isinstance(values, list) or not 1 <= len(values) <= 64:
+            raise ValueError(
+                f"Windows build inputs require explicit {name} directories"
+            )
+        for value in values:
+            directory = Path(value)
+            if not directory.is_absolute() or not directory.is_dir() or ";" in value:
+                raise ValueError(f"Invalid Windows {name} directory")
+        environment[name] = os.pathsep.join(values)
+    return environment, inputs