From a0efe16f10507816c5073f30500913292334ae78 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 1 Aug 2003 01:10:58 +0000
Subject: [PATCH] (_AS_UNSET_PREPARE): Work around a bug in Bash 2.01.  Problem
 reported by Brian Gough in
 <http://mail.gnu.org/archive/html/bug-autoconf/2003-07/msg00106.html>.

---
 lib/m4sugar/m4sh.m4 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/m4sugar/m4sh.m4 b/lib/m4sugar/m4sh.m4
index e19afb91..9826b538 100644
--- a/lib/m4sugar/m4sh.m4
+++ b/lib/m4sugar/m4sh.m4
@@ -276,9 +276,11 @@ fi
 # _AS_UNSET_PREPARE
 # -----------------
 # AS_UNSET depends upon $as_unset: compute it.
+# Use MAIL to trigger a bug in Bash 2.01;
+# the "|| exit" suppresses the resulting "Segmentation fault" message.
 m4_defun([_AS_UNSET_PREPARE],
 [# Support unset when possible.
-if (as_foo=foo; unset as_foo) >/dev/null 2>&1; then
+if ((MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
   as_unset=unset
 else
   as_unset=false
-- 
2.47.2