#!/usr/bin/env python
#===----------------------------------------------------------------------===##
#
# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
# See https://llvm.org/LICENSE.txt for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#
#===----------------------------------------------------------------------===##

import os
import sys

def print_and_exit(msg):
    sys.stderr.write(msg + '\n')
    sys.exit(1)

def usage_and_exit():
    print_and_exit("Usage: ./gen_link_script.py [--help] [--dryrun] <path/to/libcxx.so> <public_libs>...")

def help_and_exit():
    help_msg = \
"""Usage

  gen_link_script.py [--help] [--dryrun] <path/to/libcxx.so> <public_libs>...

  Generate a linker script that links libc++ to the proper ABI library.
  The script replaces the specified libc++ symlink.
  An example script for c++abi would look like "INPUT(libc++.so.1 -lc++abi)".

Arguments
  <path/to/libcxx.so> - The top level symlink to the versioned libc++ shared
                        library. This file is replaced with a linker script.
  <public_libs>       - List of library names to include in linker script.

Exit Status:
  0 if OK,
  1 if the action failed.
"""
    print_and_exit(help_msg)

def parse_args():
    args = list(sys.argv)
    del args[0]
    if len(args) == 0:
        usage_and_exit()
    if args[0] == '--help':
        help_and_exit()
    dryrun = '--dryrun' == args[0]
    if dryrun:
        del args[0]
    if len(args) < 2:
        usage_and_exit()
    symlink_file = args[0]
    public_libs = args[1:]
    return dryrun, symlink_file, public_libs

def main():
    dryrun, symlink_file, public_libs = parse_args()

    # Check that the given libc++.so file is a valid symlink.
    if not os.path.islink(symlink_file):
        print_and_exit("symlink file %s is not a symlink" % symlink_file)

    # Read the symlink so we know what libc++ to link to in the linker script.
    linked_libcxx = os.readlink(symlink_file)

    # Prepare the list of public libraries to link.
    public_libs = ['-l%s' % l for l in public_libs]

    # Generate the linker script contents and print the script and destination
    # information.
    contents = "INPUT(%s %s)" % (linked_libcxx, ' '.join(public_libs))
    print("GENERATING SCRIPT: '%s' as file %s" % (contents, symlink_file))

    # Remove the existing libc++ symlink and replace it with the script.
    if not dryrun:
        os.unlink(symlink_file)
        with open(symlink_file, 'w') as f:
            f.write(contents + "\n")


if __name__ == '__main__':
    main()