From: Bruno Haible <bruno@clisp.org>
Date: Sat, 27 Jun 2020 22:40:04 +0000 (+0200)
Subject: fatal-signal: Make multithread-safe.
X-Git-Tag: v1.0~3953
X-Git-Url: https://gitweb.git.savannah.gnu.org/gitweb/?a=commitdiff_plain;h=447062a6999c2df9cd35d6c4297dc1a55bd39cd7;p=gnulib.git

fatal-signal: Make multithread-safe.

* lib/fatal-signal.c (at_fatal_signal): Don't free the old actions array.
---

diff --git a/ChangeLog b/ChangeLog
index 7e046bc402..12dadaaa36 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2020-06-27  Bruno Haible  <bruno@clisp.org>
+
+	fatal-signal: Make multithread-safe.
+	* lib/fatal-signal.c (at_fatal_signal): Don't free the old actions array.
+
 2020-06-27  Bruno Haible  <bruno@clisp.org>
 
 	clean-temp: Don't force deletion of temporary files on native Windows.
diff --git a/lib/fatal-signal.c b/lib/fatal-signal.c
index 975393b4a0..c6f8dacbde 100644
--- a/lib/fatal-signal.c
+++ b/lib/fatal-signal.c
@@ -239,8 +239,15 @@ at_fatal_signal (action_t action)
       actions = new_actions;
       actions_allocated = new_actions_allocated;
       /* Now we can free the old actions array.  */
+      /* No, we can't do that.  If fatal_signal_handler is running in a
+         different thread and has already fetched the actions pointer (getting
+         old_actions) but not yet accessed its n-th element, that thread may
+         crash when accessing an element of the already freed old_actions
+         array.  */
+      #if 0
       if (old_actions != static_actions)
         free (old_actions);
+      #endif
     }
   /* The two uses of 'volatile' in the types above (and ISO C 99 section
      5.1.2.3.(5)) ensure that we increment the actions_count only after