From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 1 Dec 2005 21:02:40 +0000 (+0000)
Subject: * doc/autoconf.texi (Shellology): Document eval $? problem
X-Git-Tag: AUTOCONF-2.59c~220
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=599d7e2936e9f435bc293ee0a87a2723112b080c;p=thirdparty%2Fautoconf.git

* doc/autoconf.texi (Shellology): Document eval $? problem
with ash.
(Limitations of Builtins): Likewise.
---

diff --git a/ChangeLog b/ChangeLog
index b0db338b3..90ff5103d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2005-12-01  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* doc/autoconf.texi (Shellology): Document eval $? problem
+	with ash.
+	(Limitations of Builtins): Likewise.
+
 2005-11-10  Ralf Wildenhues  <Ralf.Wildenhues@gmx.de>
 
 	* lib/autoconf/status.m4 (_AC_OUTPUT_CONFIG_STATUS): Pass
@@ -62,7 +68,7 @@
 2005-10-21  Stepan Kasal  <kasal@ucw.cz>
 
 	* lib/autoconf/status.m4 (_AC_OUTPUT_FILES_PREPARE): When determining,
-	the delimiter CEOF$ac_eof: fix quoting of CEOF[0-9]* and modify the 
+	the delimiter CEOF$ac_eof: fix quoting of CEOF[0-9]* and modify the
 	code so that the most common case requires less forks.
 
 2005-10-20  Stepan Kasal  <kasal@ucw.cz>
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 88a42e737..618f38cf0 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -9783,13 +9783,16 @@ To be compatible with Ash 0.2:
 
 @itemize @minus
 @item
-don't use @samp{$?} after expanding empty or unset variables:
+don't use @samp{$?} after expanding empty or unset variables,
+or at the start of an @command{eval}:
 
 @example
 foo=
 false
 $foo
-echo "Don't use it: $?"
+echo "Do not use it: $?"
+false
+eval 'echo "Do not use it: $?"'
 @end example
 
 @item
@@ -11121,6 +11124,25 @@ EOF
 @end example
 
 
+@item @command{eval}
+@c -----------------
+@prindex @command{eval}
+In some shell implementations (e.g., @command{ash}, OpenBSD 3.8
+@command{sh}, @command{pdksh} v5.2.14 99/07/13.2, and @command{zsh}
+4.2.5), the arguments of @samp{eval} are evaluated in a context where
+@samp{$?} is 0, so they exhibit behavior like this:
+
+@example
+$ false; eval 'echo $?'
+0
+@end example
+
+The correct behavior here is to assign a nonzero value to @samp{foo},
+but portable scripts should not rely on this.
+
+You should not rely on @code{LINENO} within @command{eval}.
+@xref{Special Shell Variables}.
+
 @item @command{exit}
 @c -----------------
 @prindex @command{exit}