gh-96652: Fix faulthandler chained signal without sigaction() (GH-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. (cherry picked from commit c580a81) Co-authored-by: Victor Stinner <[email protected]>
python · Sep 8, 2022 · 3d6e6be · 3d6e6be
1 parent a3d5ecb
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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
@@ -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
@@ -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);