From f14bf539c26d186f75aa6da900660527358533de Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Tue, 24 Mar 2026 00:47:47 +0100
Subject: [PATCH] gh-146202: Create tmp_dir in regrtest worker (GH-146347)

Create tmp_dir in libregrtest.worker since the directory can be
different than the --tempdir directory.
(cherry picked from commit bcff99cb3f3b887a08c4f0ace1279ced38dd9e62)

Co-authored-by: Victor Stinner <vstinner@python.org>
---
 Lib/test/libregrtest/utils.py                               | 6 ------
 Lib/test/libregrtest/worker.py                              | 3 +++
 .../Tests/2026-03-24-00-15-58.gh-issue-146202.LgH6Bj.rst    | 3 +++
 3 files changed, 6 insertions(+), 6 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Tests/2026-03-24-00-15-58.gh-issue-146202.LgH6Bj.rst

diff --git a/Lib/test/libregrtest/utils.py b/Lib/test/libregrtest/utils.py
index f12cec944fd3bf..c0e8c090670bc3 100644
--- a/Lib/test/libregrtest/utils.py
+++ b/Lib/test/libregrtest/utils.py
@@ -466,12 +466,6 @@ def get_temp_dir(tmp_dir: StrPath | None = None) -> StrPath:
                         f"unexpectedly returned {tmp_dir!r} on WASI"
                     )
                 tmp_dir = os.path.join(tmp_dir, 'build')
-
-                # When get_temp_dir() is called in a worker process,
-                # get_temp_dir() path is different than in the parent process
-                # which is not a WASI process. So the parent does not create
-                # the same "tmp_dir" than the test worker process.
-                os.makedirs(tmp_dir, exist_ok=True)
         else:
             tmp_dir = tempfile.gettempdir()
 
diff --git a/Lib/test/libregrtest/worker.py b/Lib/test/libregrtest/worker.py
index e0627c4adc0107..c1c7922ae0c651 100644
--- a/Lib/test/libregrtest/worker.py
+++ b/Lib/test/libregrtest/worker.py
@@ -112,6 +112,9 @@ def main() -> NoReturn:
     worker_json = sys.argv[1]
 
     tmp_dir = get_temp_dir()
+    # get_temp_dir() can be different in the worker and the parent process.
+    # For example, if --tempdir option is used.
+    os.makedirs(tmp_dir, exist_ok=True)
     work_dir = get_work_dir(tmp_dir, worker=True)
 
     with exit_timeout():
diff --git a/Misc/NEWS.d/next/Tests/2026-03-24-00-15-58.gh-issue-146202.LgH6Bj.rst b/Misc/NEWS.d/next/Tests/2026-03-24-00-15-58.gh-issue-146202.LgH6Bj.rst
new file mode 100644
index 00000000000000..ef869fe2617256
--- /dev/null
+++ b/Misc/NEWS.d/next/Tests/2026-03-24-00-15-58.gh-issue-146202.LgH6Bj.rst
@@ -0,0 +1,3 @@
+Fix a race condition in regrtest: make sure that the temporary directory is
+created in the worker process. Previously, temp_cwd() could fail on Windows if
+the "build" directory was not created.  Patch by Victor Stinner.