From c580a81af91af4b9df85e466f8b48c3c9c86c3df Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Thu, 8 Sep 2022 12:20:22 +0200
Subject: [PATCH] gh-96652: Fix faulthandler chained signal without sigaction()
(#96666)
Fix the faulthandler implementation of faulthandler.register(signal,
chain=True) if the sigaction() function is not available: don't call
the previous signal handler if it's NULL.
---
.../next/Library/2022-09-07-22-49-37.gh-issue-96652.YqOKxI.rst | 3 +++
Modules/faulthandler.c | 2 +-
2 files changed, 4 insertions(+), 1 deletion(-)
create mode 100644 Misc/NEWS.d/next/Library/2022-09-07-22-49-37.gh-issue-96652.YqOKxI.rst
diff --git a/Misc/NEWS.d/next/Library/2022-09-07-22-49-37.gh-issue-96652.YqOKxI.rst b/Misc/NEWS.d/next/Library/2022-09-07-22-49-37.gh-issue-96652.YqOKxI.rst
new file mode 100644
index 00000000000..1d04db7b2a2
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2022-09-07-22-49-37.gh-issue-96652.YqOKxI.rst
@@ -0,0 +1,3 @@
+Fix the faulthandler implementation of ``faulthandler.register(signal,
+chain=True)`` if the ``sigaction()`` function is not available: don't call
+the previous signal handler if it's NULL. Patch by Victor Stinner.
diff --git a/Modules/faulthandler.c b/Modules/faulthandler.c
index b36268782bd..8b5cf276afc 100644
--- a/Modules/faulthandler.c
+++ b/Modules/faulthandler.c
@@ -862,7 +862,7 @@ faulthandler_user(int signum)
errno = save_errno;
}
#else
- if (user->chain) {
+ if (user->chain && user->previous != NULL) {
errno = save_errno;
/* call the previous signal handler */
user->previous(signum);
--
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