1 files changed, 82 insertions, 0 deletions
diff --git a/build/clang-plugin/ThreadAllows.py b/build/clang-plugin/ThreadAllows.py
new file mode 100644
index 0000000000..f3e1ee894c
--- /dev/null
+++ b/build/clang-plugin/ThreadAllows.py
@@ -0,0 +1,82 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+import json
+import os
+import posixpath
+from os import PathLike
+
+# `typing.Literal` not available until Python 3.8;
+# `typing_extensions` not generally available here
+from typing import Iterable, Set
+
+FIRST_LINE = "// This file was generated by {}. DO NOT EDIT.".format(
+    # `posixpath` for forward slashes, for presentation purposes
+    posixpath.relpath(__file__, os.getenv("TOPSRCDIR", "/"))
+)
+
+
+def generate_allowed_items(
+    which: str,  # should be: Literal["files", "names"],
+    paths: Iterable[PathLike],
+) -> str:
+    def remove_trailing_comment(s: str) -> str:
+        return s[0 : s.find("#")]
+
+    def read_items_from_path(path: PathLike) -> Set[str]:
+        out = set()
+        with open(path) as file:
+            for line in file.readlines():
+                line = remove_trailing_comment(line).strip()
+                if not line:
+                    continue  # comment or empty line; discard
+                out.add(line)
+        return out
+
+    allowed = set().union(*(read_items_from_path(path) for path in paths))
+    # BUG: `json.dumps` may not correctly handle use of the quote character in
+    #   thread names
+    allowed_list_s = ",\n  ".join(json.dumps(elem) for elem in sorted(allowed))
+
+    return f"""\
+static const char *allow_thread_{which}[] = {{
+  {allowed_list_s}
+}};"""
+
+
+def generate_allows(
+    *, allowed_names: Iterable[PathLike], allowed_files: Iterable[PathLike]
+) -> str:
+    """
+    This function reads in the specified sets of files -- ordinarily,
+    ["ThreadAllows.txt"] and ["ThreadFileAllows.txt"] -- and generates the text
+    of a header file containing two arrays with their contents, for inclusion by
+    the thread-name checker.
+
+    The checker will reject the creation of any thread via NS_NewNamedThread
+    unless either:
+      - the thread's name is a literal string which is found in the set of
+        allowed thread names; or
+      - the thread's creation occurs within a file which is found in the set of
+        unchecked files.
+
+    The latter condition exists mostly for the definition of NS_NewNamedThread,
+    but there also exist a few cases where the thread name is dynamically
+    computed (and so can't be checked).
+    """
+    output_string = (
+        FIRST_LINE
+        + "\n\n"
+        + generate_allowed_items("files", allowed_files)
+        + "\n\n"
+        + generate_allowed_items("names", allowed_names)
+        + "\n"
+    )
+    return output_string
+
+
+# Entry point used by build/clang-plugin/moz.build (q.v.).
+def generate_file(output, allowed_names, allowed_files):
+    output.write(
+        generate_allows(allowed_names=[allowed_names], allowed_files=[allowed_files])
+    )