22-as-unset.patch

[Akim Demaille]

Index: 0.491/ChangeLog
from  Akim Demaille  <address@hidden>
        * m4sh.m4 (_AS_UNSET_PREPARE): New macro, eved from
        _AC_INIT_PREPARE_ENVIRONMENT, and fixed: set `FOO' before trying
        to unset it: `unset' exits 1 if the variable is not defined.
        (AS_UNSET): Require it.  Use `as_unset' not `ac_unset'.
        * acgeneral.m4 (_AC_INIT_PREPARE_ENVIRONMENT): Use it.
        
        
Index: 0.491/acgeneral.m4
--- 0.491/acgeneral.m4 Wed, 01 Nov 2000 14:06:01 +0100 akim (ace/27_acgeneral. 
1.169.8.80 666)
+++ 0.492(w)/acgeneral.m4 Wed, 01 Nov 2000 14:38:57 +0100 akim 
(ace/27_acgeneral. 1.169.8.81 666)
@@ -1373,12 +1373,7 @@
   set -o posix
 fi
 
-# Support unset when possible.
-if (unset FOO) >/dev/null 2>&1; then
-  ac_unset=unset
-else
-  ac_unset=false
-fi
+_AS_UNSET_PREPARE
 
 # NLS nuisances.
 AS_UNSET([LANG],        [C])
Index: 0.491/m4sh.m4
--- 0.491/m4sh.m4 Wed, 01 Nov 2000 14:25:34 +0100 akim (ace/b/41_m4sh.m4 1.3 
644)
+++ 0.492(w)/m4sh.m4 Wed, 01 Nov 2000 14:37:51 +0100 akim (ace/b/41_m4sh.m4 1.3 
644)
@@ -77,12 +77,26 @@
 ])# AS_IFELSE
 
 
+# _AS_UNSET_PREPARE
+# -----------------
+# AS_UNSET depends upon $as_unset: compute it.
+m4_defun([_AS_UNSET_PREPARE],
+[# Support unset when possible.
+if (FOO=FOO; unset FOO) >/dev/null 2>&1; then
+  as_unset=unset
+else
+  as_unset=false
+fi
+])
+
+
 # AS_UNSET(VAR, [VALUE-IF-UNSET-NOT-SUPPORTED = `'])
 # --------------------------------------------------
 # Try to unset the env VAR, otherwise set it to
 # VALUE-IF-UNSET-NOT-SUPPORTED.  `ac_unset' must have been computed.
-m4_define([AS_UNSET],
-[$ac_unset $1 || test "${$1+set}" != set || { $1=$2; export $1; }])
+m4_defun([AS_UNSET],
+[m4_require([_AS_UNSET_PREPARE])dnl
+$as_unset $1 || test "${$1+set}" != set || { $1=$2; export $1; }])