def main(args=None):
    """ Entry point when executed from command line.
    You can use zxb.py as a module with import, and this
    function won't be executed.
    """
    api.config.init()
    zxbpp.init()
    zxbparser.init()
    arch.zx48k.backend.init()
    arch.zx48k.Translator.reset()
    asmparse.init()

    # ------------------------------------------------------------
    # Command line parsing
    # ------------------------------------------------------------
    parser = argparse.ArgumentParser(prog='zxb')
    parser.add_argument('PROGRAM', type=str,
                        help='BASIC program file')
    parser.add_argument('-d', '--debug', dest='debug', default=OPTIONS.Debug.value, action='count',
                        help='Enable verbosity/debugging output. Additional -d increase verbosity/debug level')
    parser.add_argument('-O', '--optimize', type=int, default=OPTIONS.optimization.value,
                        help='Sets optimization level. '
                             '0 = None (default level is {0})'.format(OPTIONS.optimization.value))
    parser.add_argument('-o', '--output', type=str, dest='output_file', default=None,
                        help='Sets output file. Default is input filename with .bin extension')
    parser.add_argument('-T', '--tzx', action='store_true',
                        help="Sets output format to tzx (default is .bin)")
    parser.add_argument('-t', '--tap', action='store_true',
                        help="Sets output format to tap (default is .bin)")
    parser.add_argument('-B', '--BASIC', action='store_true', dest='basic',
                        help="Creates a BASIC loader which loads the rest of the CODE. Requires -T ot -t")
    parser.add_argument('-a', '--autorun', action='store_true',
                        help="Sets the program to be run once loaded")
    parser.add_argument('-A', '--asm', action='store_true',
                        help="Sets output format to asm")
    parser.add_argument('-S', '--org', type=str, default=str(OPTIONS.org.value),
                        help="Start of machine code. By default %i" % OPTIONS.org.value)
    parser.add_argument('-e', '--errmsg', type=str, dest='stderr', default=OPTIONS.StdErrFileName.value,
                        help='Error messages file (standard error console by default)')
    parser.add_argument('--array-base', type=int, default=OPTIONS.array_base.value,
                        help='Default lower index for arrays ({0} by default)'.format(OPTIONS.array_base.value))
    parser.add_argument('--string-base', type=int, default=OPTIONS.string_base.value,
                        help='Default lower index for strings ({0} by default)'.format(OPTIONS.array_base.value))
    parser.add_argument('-Z', '--sinclair', action='store_true',
                        help='Enable by default some more original ZX Spectrum Sinclair BASIC features: ATTR, SCREEN$, '
                             'POINT')
    parser.add_argument('-H', '--heap-size', type=int, default=OPTIONS.heap_size.value,
                        help='Sets heap size in bytes (default {0} bytes)'.format(OPTIONS.heap_size.value))
    parser.add_argument('--debug-memory', action='store_true',
                        help='Enables out-of-memory debug')
    parser.add_argument('--debug-array', action='store_true',
                        help='Enables array boundary checking')
    parser.add_argument('--strict-bool', action='store_true',
                        help='Enforce boolean values to be 0 or 1')
    parser.add_argument('--enable-break', action='store_true',
                        help='Enables program execution BREAK detection')
    parser.add_argument('-E', '--emit-backend', action='store_true',
                        help='Emits backend code instead of ASM or binary')
    parser.add_argument('--explicit', action='store_true',
                        help='Requires all variables and functions to be declared before used')
    parser.add_argument('-D', '--define', type=str, dest='defines', action='append',
                        help='Defines de given macro. Eg. -D MYDEBUG or -D NAME=Value')
    parser.add_argument('-M', '--mmap', type=str, dest='memory_map', default=None,
                        help='Generate label memory map')
    parser.add_argument('-i', '--ignore-case', action='store_true',
                        help='Ignore case. Makes variable names are case insensitive')
    parser.add_argument('-I', '--include-path', type=str, default='',
                        help='Add colon separated list of directories to add to include path. e.g. -I dir1:dir2')
    parser.add_argument('--strict', action='store_true',
                        help='Enables strict mode. Force explicit type declaration')
    parser.add_argument('--headerless', action='store_true',
                        help='Header-less mode: omit asm prologue and epilogue')
    parser.add_argument('--version', action='version', version='%(prog)s {0}'.format(VERSION))
    parser.add_argument('--parse-only', action='store_true',
                        help='Only parses to check for syntax and semantic errors')
    parser.add_argument('--append-binary', default=[], action='append',
                        help='Appends binary to tape file (only works with -t or -T)')
    parser.add_argument('--append-headless-binary', default=[], action='append',
                        help='Appends binary to tape file (only works with -t or -T)')

    options = parser.parse_args(args=args)

    # ------------------------------------------------------------
    # Setting of internal parameters according to command line
    # ------------------------------------------------------------

    OPTIONS.Debug.value = options.debug
    OPTIONS.optimization.value = options.optimize
    OPTIONS.outputFileName.value = options.output_file
    OPTIONS.StdErrFileName.value = options.stderr
    OPTIONS.array_base.value = options.array_base
    OPTIONS.string_base.value = options.string_base
    OPTIONS.Sinclair.value = options.sinclair
    OPTIONS.heap_size.value = options.heap_size
    OPTIONS.memoryCheck.value = options.debug_memory
    OPTIONS.strictBool.value = options.strict_bool or OPTIONS.Sinclair.value
    OPTIONS.arrayCheck.value = options.debug_array
    OPTIONS.emitBackend.value = options.emit_backend
    OPTIONS.enableBreak.value = options.enable_break
    OPTIONS.explicit.value = options.explicit
    OPTIONS.memory_map.value = options.memory_map
    OPTIONS.strict.value = options.strict
    OPTIONS.headerless.value = options.headerless

    OPTIONS.org.value = api.utils.parse_int(options.org)
    if OPTIONS.org.value is None:
        parser.error("Invalid --org option '{}'".format(options.org))

    if options.defines:
        for i in options.defines:
            name, val = tuple(i.split('=', 1))
            OPTIONS.__DEFINES.value[name] = val
            zxbpp.ID_TABLE.define(name, lineno=0)

    if OPTIONS.Sinclair.value:
        OPTIONS.array_base.value = 1
        OPTIONS.string_base.value = 1
        OPTIONS.strictBool.value = True
        OPTIONS.case_insensitive.value = True

    if options.ignore_case:
        OPTIONS.case_insensitive.value = True

    debug.ENABLED = OPTIONS.Debug.value

    if int(options.tzx) + int(options.tap) + int(options.asm) + int(options.emit_backend) + \
            int(options.parse_only) > 1:
        parser.error("Options --tap, --tzx, --emit-backend, --parse-only and --asm are mutually exclusive")
        return 3

    if options.basic and not options.tzx and not options.tap:
        parser.error('Option --BASIC and --autorun requires --tzx or tap format')
        return 4

    if options.append_binary and not options.tzx and not options.tap:
        parser.error('Option --append-binary needs either --tap or --tzx')
        return 5

    OPTIONS.use_loader.value = options.basic
    OPTIONS.autorun.value = options.autorun

    if options.tzx:
        OPTIONS.output_file_type.value = 'tzx'
    elif options.tap:
        OPTIONS.output_file_type.value = 'tap'
    elif options.asm:
        OPTIONS.output_file_type.value = 'asm'
    elif options.emit_backend:
        OPTIONS.output_file_type.value = 'ic'

    args = [options.PROGRAM]
    if not os.path.exists(options.PROGRAM):
        parser.error("No such file or directory: '%s'" % args[0])
        return 2

    if OPTIONS.memoryCheck.value:
        OPTIONS.__DEFINES.value['__MEMORY_CHECK__'] = ''
        zxbpp.ID_TABLE.define('__MEMORY_CHECK__', lineno=0)

    if OPTIONS.arrayCheck.value:
        OPTIONS.__DEFINES.value['__CHECK_ARRAY_BOUNDARY__'] = ''
        zxbpp.ID_TABLE.define('__CHECK_ARRAY_BOUNDARY__', lineno=0)

    OPTIONS.include_path.value = options.include_path
    OPTIONS.inputFileName.value = zxbparser.FILENAME = \
        os.path.basename(args[0])

    if not OPTIONS.outputFileName.value:
        OPTIONS.outputFileName.value = \
            os.path.splitext(os.path.basename(OPTIONS.inputFileName.value))[0] + os.path.extsep + \
            OPTIONS.output_file_type.value

    if OPTIONS.StdErrFileName.value:
        OPTIONS.stderr.value = open_file(OPTIONS.StdErrFileName.value, 'wt', 'utf-8')

    zxbpp.setMode('basic')
    zxbpp.main(args)

    if gl.has_errors:
        debug.__DEBUG__("exiting due to errors.")
        return 1  # Exit with errors

    input_ = zxbpp.OUTPUT
    zxbparser.parser.parse(input_, lexer=zxblex.lexer, tracking=True,
                           debug=(OPTIONS.Debug.value > 2))
    if gl.has_errors:
        debug.__DEBUG__("exiting due to errors.")
        return 1  # Exit with errors

    # Optimizations
    optimizer = api.optimize.OptimizerVisitor()
    optimizer.visit(zxbparser.ast)

    # Emits intermediate code
    translator = arch.zx48k.Translator()
    translator.visit(zxbparser.ast)

    if gl.DATA_IS_USED:
        gl.FUNCTIONS.extend(gl.DATA_FUNCTIONS)

    # This will fill MEMORY with pending functions
    func_visitor = arch.zx48k.FunctionTranslator(gl.FUNCTIONS)
    func_visitor.start()

    # Emits data lines
    translator.emit_data_blocks()
    # Emits default constant strings
    translator.emit_strings()
    # Emits jump tables
    translator.emit_jump_tables()

    if OPTIONS.emitBackend.value:
        with open_file(OPTIONS.outputFileName.value, 'wt', 'utf-8') as output_file:
            for quad in translator.dumpMemory(backend.MEMORY):
                output_file.write(str(quad) + '\n')

            backend.MEMORY[:] = []  # Empties memory
            # This will fill MEMORY with global declared variables
            translator = arch.zx48k.VarTranslator()
            translator.visit(zxbparser.data_ast)

            for quad in translator.dumpMemory(backend.MEMORY):
                output_file.write(str(quad) + '\n')
        return 0  # Exit success

    # Join all lines into a single string and ensures an INTRO at end of file
    asm_output = backend.emit(backend.MEMORY)
    asm_output = optimize(asm_output) + '\n'

    asm_output = asm_output.split('\n')
    for i in range(len(asm_output)):
        tmp = backend.ASMS.get(asm_output[i], None)
        if tmp is not None:
            asm_output[i] = '\n'.join(tmp)

    asm_output = '\n'.join(asm_output)

    # Now filter them against the preprocessor again
    zxbpp.setMode('asm')
    zxbpp.OUTPUT = ''
    zxbpp.filter_(asm_output, args[0])

    # Now output the result
    asm_output = zxbpp.OUTPUT.split('\n')
    get_inits(asm_output)  # Find out remaining inits
    backend.MEMORY[:] = []

    # This will fill MEMORY with global declared variables
    translator = arch.zx48k.VarTranslator()
    translator.visit(zxbparser.data_ast)
    if gl.has_errors:
        debug.__DEBUG__("exiting due to errors.")
        return 1  # Exit with errors

    tmp = [x for x in backend.emit(backend.MEMORY) if x.strip()[0] != '#']
    asm_output += tmp
    asm_output = backend.emit_start() + asm_output
    asm_output += backend.emit_end(asm_output)

    if options.asm:  # Only output assembler file
        with open_file(OPTIONS.outputFileName.value, 'wt', 'utf-8') as output_file:
            output(asm_output, output_file)
    elif not options.parse_only:
        fout = StringIO()
        output(asm_output, fout)
        asmparse.assemble(fout.getvalue())
        fout.close()
        asmparse.generate_binary(OPTIONS.outputFileName.value, OPTIONS.output_file_type.value,
                                 binary_files=options.append_binary,
                                 headless_binary_files=options.append_headless_binary)
        if gl.has_errors:
            return 5  # Error in assembly

    if OPTIONS.memory_map.value:
        with open_file(OPTIONS.memory_map.value, 'wt', 'utf-8') as f:
            f.write(asmparse.MEMORY.memory_map)

    return gl.has_errors