scripts/msvc_extract_private_symbols.py

"""A tool for extracting a list of private lldb symbols to export for MSVC.

When exporting symbols from a dll or exe we either need to mark the symbols in
the source code as __declspec(dllexport) or supply a list of symbols to the
linker. Private symbols in LLDB don't explicitly specific dllexport, so we
automate that by examining the symbol table.
"""

import argparse
import os
import re
import subprocess
import sys


def extract_symbols(nm_path: str, lib: str):
    """Extract all of the private lldb symbols from the given path to llvm-nm and
    library to extract from."""

    # Matches mangled symbols containing 'lldb_private'.
    lldb_sym_re = r"[0-9a-zA-Z]* [BT] (?P<symbol>[?]+[^?].*lldb_private.*)"

    # '-g' means we only get global symbols.
    # '-p' do not waste time sorting the symbols.
    process = subprocess.Popen(
        [nm_path, "-g", "-p", lib],
        bufsize=1,
        stdout=subprocess.PIPE,
        stdin=subprocess.PIPE,
        universal_newlines=True,
    )
    process.stdin.close()

    lldb_symbols = set()
    for line in process.stdout:
        match = re.match(lldb_sym_re, line)
        if match:
            symbol = match.group("symbol")
            assert (
                symbol.count(" ") == 0
            ), "Regex matched too much, probably got undecorated name as well"
            # Deleting destructors start with ?_G or ?_E and can be discarded
            # because link.exe gives you a warning telling you they can't be
            # exported if you don't.
            if symbol.startswith("??_G") or symbol.startswith("??_E"):
                continue
            lldb_symbols.add(symbol)

    return lldb_symbols


def main():
    parser = argparse.ArgumentParser(description="Generate LLDB dll exports")
    parser.add_argument(
        "-o", metavar="file", type=str, help="The name of the resultant export file."
    )
    parser.add_argument("--nm", help="Path to the llvm-nm executable.")
    parser.add_argument(
        "libs",
        metavar="lib",
        type=str,
        nargs="+",
        help="The libraries to extract symbols from.",
    )
    args = parser.parse_args()

    # Get the list of libraries to extract symbols from
    libs = list()
    for lib in args.libs:
        # When invoked by cmake the arguments are the cmake target names of the
        # libraries, so we need to add .lib/.a to the end and maybe lib to the
        # start to get the filename. Also allow objects.
        suffixes = [".lib", ".a", ".obj", ".o"]
        if not any([lib.endswith(s) for s in suffixes]):
            for suffix in suffixes:
                if os.path.exists(lib + suffix):
                    lib = lib + suffix
                    break
                if os.path.exists("lib" + lib + suffix):
                    lib = "lib" + lib + suffix
                    break
        if not any([lib.endswith(s) for s in suffixes]):
            print(
                "Unknown extension type for library argument: " + lib, file=sys.stderr
            )
            exit(1)
        libs.append(lib)

    # Extract symbols from the input libraries.
    symbols = set()
    for lib in libs:
        for sym in list(extract_symbols(args.nm, lib)):
            symbols.add(sym)

    # Write out the symbols to the output file.
    with open(args.o, "w", newline="") as f:
        for s in sorted(symbols):
            f.write(f"{s}\n")


if __name__ == "__main__":
    main()