Function create_thin_archive

ci/wasm_build_library.py:392–461

Create a thin archive from object files. Thin archives store references to object files instead of copying them, resulting in faster archive creation and smaller archive size. Args: emar: Archiver command (e.g., 'clang-tool-chain-emar') object_files: List of .o fil

(
    emar: str,
    object_files: list[Path],
    output_path: Path,
    verbose: bool = False,
)

def create_thin_archive(
    emar: str,
    object_files: list[Path],
    output_path: Path,
    verbose: bool = False,
) -> int:
    """
    Create a thin archive from object files.

    Thin archives store references to object files instead of copying them,
    resulting in faster archive creation and smaller archive size.

    Args:
        emar: Archiver command (e.g., 'clang-tool-chain-emar')
        object_files: List of .o files to include
        output_path: Output .a archive path
        verbose: Enable verbose output

    Returns:
        Exit code (0 = success)
    """
    print(f"Creating thin archive: {output_path.name}...")

    if not object_files:
        print("✗ No object files to archive")
        return 1

    # Ensure output directory exists
    output_path.parent.mkdir(parents=True, exist_ok=True)

    # Remove existing archive to prevent stale objects from persisting.
    # The 'r' flag in emar inserts/replaces, so old entries would remain.
    if output_path.exists():
        output_path.unlink()

    # Create response file for object list (avoid command line length limits)
    response_file = BUILD_DIR / "archive_objects.rsp"
    with open(response_file, "w") as f:
        for obj in object_files:
            f.write(f"{obj}\n")

    # Build archive command
    # rcsT flags:
    #   r = insert/replace files in archive
    #   c = create archive if it doesn't exist
    #   s = write an index (required for linking)
    #   T = create thin archive (references instead of copies)
    cmd = [
        emar,
        "rcsT",
        str(output_path),
        f"@{response_file}",
    ]

    if verbose:
        print(f"Command: {' '.join(cmd)}")

    result = subprocess.run(cmd, cwd=PROJECT_ROOT)