link-order.py

#!/usr/bin/env python3

"""
Compute link order
"""

import sys
from pathlib import Path
import typing
from typing import Set, NamedTuple
import subprocess

Symbol = str
class Syms(NamedTuple):
    defined: Set[Symbol]
    referenced: Set[Symbol]

def get_syms(obj):
    out = subprocess.check_output(['nm', '-g', '--format=posix', obj], encoding='ASCII')
    defined = set()
    referenced = set()
    for l in out.split('\n'):
        parts = l.split(' ')
        if len(parts) >= 2:
            symbol = parts[0]
            state = parts[1]
            if state == 'U':
                referenced.add(symbol)
            else:
                defined.add(symbol)

    referenced.difference_update(defined)
    return Syms(defined, referenced)

def dump_deps(objects: Set[str], file: typing.TextIO):
    obj_symbols = {obj: get_syms(obj) for obj in objects}
    for obj, syms in obj_symbols.items():
        for sym in syms.defined:
            print(f'{sym} @{obj}', file=file)
        for sym in syms.referenced:
            print(f'@{obj} {sym}', file=file)

def link_order(objects):
    p = subprocess.Popen(['tsort'], stdin=subprocess.PIPE, encoding='ASCII')
    dump_deps(objects, p.stdin)
    p.stdin.close()
    p.wait()
    
def main():
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('object', nargs='+')
    parser.add_argument('--raw', action='store_true')
    args = parser.parse_args()
    if args.raw:
        dump_deps(args.object, sys.stdout)
    else:
        link_order(args.object)

if __name__ == '__main__':
    main()