Function invalidate_stale_pch

ci/compile_pch.py:207–251

Delete a PCH file if its input files have changed since it was built. Uses the ``.d.cache`` and ``.input_hash`` files saved by previous builds to detect when a header dependency has been modified. If the hash doesn't match, the PCH and hash file are removed so Ninja is forced to rebuil

(pch_file: Path)

def invalidate_stale_pch(pch_file: Path) -> None:
    """Delete a PCH file if its input files have changed since it was built.

    Uses the ``.d.cache`` and ``.input_hash`` files saved by previous builds
    to detect when a header dependency has been modified.  If the hash doesn't
    match, the PCH and hash file are removed so Ninja is forced to rebuild.

    This works around a Ninja limitation on Windows where backslash paths in
    depfiles can cause Ninja to miss dependency changes.
    """
    if not pch_file.exists():
        return

    saved_depfile = pch_file.with_name(pch_file.name.replace(".pch", ".d.cache"))
    hash_file = Path(str(pch_file) + ".input_hash")
    if not saved_depfile.exists() or not hash_file.exists():
        # Missing tracking files means we can't verify the PCH is fresh.
        # Delete it to force a safe rebuild rather than risking a stale-PCH
        # compiler error that would fail the entire build.
        print(
            f"PCH tracking files missing — removing {pch_file.name} to force rebuild",
            file=sys.stderr,
        )
        pch_file.unlink(missing_ok=True)
        hash_file.unlink(missing_ok=True)
        return

    try:
        input_files = parse_depfile_inputs(saved_depfile)
        if not input_files:
            return
        current_hash = hash_input_files(input_files)
        stored_hash = hash_file.read_text(encoding="utf-8").strip()
        if current_hash != stored_hash:
            print(
                f"PCH inputs changed — removing stale {pch_file.name} to force rebuild",
                file=sys.stderr,
            )
            pch_file.unlink(missing_ok=True)
            hash_file.unlink(missing_ok=True)
    except KeyboardInterrupt as ki:
        handle_keyboard_interrupt(ki)
        raise
    except Exception as e:
        print(f"WARNING: PCH staleness check failed: {e}", file=sys.stderr)


def main() -> int: