def memset_padding(builder, ptr):
    """
    Fill padding bytes of the pointee with zeros.
    """
    # Load existing value
    val = builder.load(ptr)
    # Fill pointee with zeros
    memset(builder, ptr, sizeof(builder, ptr.type), 0)
    # Store value back
    builder.store(val, ptr)

    Fill padding bytes of the pointee with zeros.
    
numba/core/cgutils.py