build/clang-plugin/ThreadAllows.py

   1 # This Source Code Form is subject to the terms of the Mozilla Public
   2 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
   3 # You can obtain one at http://mozilla.org/MPL/2.0/.
   4 import json
   5 import os
   6 import posixpath
   7 from os import PathLike
   8
   9 # `typing.Literal` not available until Python 3.8;
  10 # `typing_extensions` not generally available here
  11 from typing import Iterable, Set
  12
  13 FIRST_LINE = "// This file was generated by {}. DO NOT EDIT.".format(
  14     # `posixpath` for forward slashes, for presentation purposes
  15     posixpath.relpath(__file__, os.getenv("TOPSRCDIR", "/"))
  16 )
  17
  18
  19 def generate_allowed_items(
  20     which: str,  # should be: Literal["files", "names"],
  21     paths: Iterable[PathLike],
  22 ) -> str:
  23     def remove_trailing_comment(s: str) -> str:
  24         return s[0 : s.find("#")]
  25
  26     def read_items_from_path(path: PathLike) -> Set[str]:
  27         out = set()
  28         with open(path) as file:
  29             for line in file.readlines():
  30                 line = remove_trailing_comment(line).strip()
  31                 if not line:
  32                     continue  # comment or empty line; discard
  33                 out.add(line)
  34         return out
  35
  36     allowed = set().union(*(read_items_from_path(path) for path in paths))
  37     # BUG: `json.dumps` may not correctly handle use of the quote character in
  38     #   thread names
  39     allowed_list_s = ",\n  ".join(json.dumps(elem) for elem in sorted(allowed))
  40
  41     return f"""\
  42 static const char *allow_thread_{which}[] = {{
  43   {allowed_list_s}
  44 }};"""
  45
  46
  47 def generate_allows(
  48     *, allowed_names: Iterable[PathLike], allowed_files: Iterable[PathLike]
  49 ) -> str:
  50     """
  51     This function reads in the specified sets of files -- ordinarily,
  52     ["ThreadAllows.txt"] and ["ThreadFileAllows.txt"] -- and generates the text
  53     of a header file containing two arrays with their contents, for inclusion by
  54     the thread-name checker.
  55
  56     The checker will reject the creation of any thread via NS_NewNamedThread
  57     unless either:
  58       - the thread's name is a literal string which is found in the set of
  59         allowed thread names; or
  60       - the thread's creation occurs within a file which is found in the set of
  61         unchecked files.
  62
  63     The latter condition exists mostly for the definition of NS_NewNamedThread,
  64     but there also exist a few cases where the thread name is dynamically
  65     computed (and so can't be checked).
  66     """
  67     output_string = (
  68         FIRST_LINE
  69         + "\n\n"
  70         + generate_allowed_items("files", allowed_files)
  71         + "\n\n"
  72         + generate_allowed_items("names", allowed_names)
  73         + "\n"
  74     )
  75     return output_string
  76
  77
  78 # Entry point used by build/clang-plugin/moz.build (q.v.).
  79 def generate_file(output, allowed_names, allowed_files):
  80     output.write(
  81         generate_allows(allowed_names=[allowed_names], allowed_files=[allowed_files])
  82     )