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[SCM] GNU Autoconf source repository branch, master, updated. v2.63-49-g
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From: |
Paolo Bonzini |
|
Subject: |
[SCM] GNU Autoconf source repository branch, master, updated. v2.63-49-g2079086 |
|
Date: |
Wed, 15 Oct 2008 14:07:23 +0000 |
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- Log -----------------------------------------------------------------
commit 2079086ce2fa69ee0bce8e0a9cf65f57019877b1
Author: Paolo Bonzini <address@hidden>
Date: Wed Oct 15 11:03:35 2008 +0200
Updates to shell portability documentation
* doc/autoconf.texi: Updates all references to "Portable Shell" and
"Limitations of Builtins" to use three-argument commands.
(Programming in M4sh): Document AS_ECHO, AS_ECHO_N, AS_UNSET.
(Portable Shell): Move here discussion about "Where is the POSIX
shell?" Mention that M4sh provides a SVR2 shell and takes care
of unsetting variables if necessary. Talk about M4sh and not only
Autoconf-generated scripts.
(Special Shell Variables): Talk about M4sh and not only
Autoconf-generated scripts. Don't talk about things that Autoconf
does not do. Mention problems of $LINENO with shell functions.
(Limitations of Builtins). Mention AS_ECHO and AS_ECHO_N. Move
discussion of eval bugs before discussion on proper use of eval.
Mention AS_IF. Reword why not to use "shift N". Mention "foo=;
unset foo" trick. Include M4sh code that unsets MAIL for Bash 2.01.
* NEWS: Update list of documented M4sh macros.
commit 26ba5ebd23bcee95d446181b57dac61d7163c041
Author: Paolo Bonzini <address@hidden>
Date: Tue Oct 14 07:16:48 2008 +0200
Assume a (possibly buggy) `unset' is present after a `better shell' was
found.
* lib/autoconf/general.m4 (_AC_CACHE_DUMP): Use AS_UNSET.
* lib/autoconf/programs.m4 (AC_PROG_SED): Use AS_UNSET.
* lib/m4sugar/m4sh.m4 (_AS_UNSET_PREPARE): Provide $as_unset as an
alias for AS_UNSET, for backwards compatibility.
(_AS_DETECT_BETTER_SHELL): Set BASH_ENV and ENV to /dev/null in case
the shell does not support unset.
(_AS_SHELL_SANITIZE): Work around Bash 2.01 bugs. Unset BASH_ENV.
(AS_INIT, _AS_PREPARE, AS_PREPARE): Call it.
(AS_UNSET): Assume it is there but it might fail if the variable is
not set. Use it throughout instead of $as_unset.
commit d73b293fd3508e995905a538c1725c19b2d6d846
Author: Paolo Bonzini <address@hidden>
Date: Wed Oct 15 11:02:09 2008 +0200
Turn AS_SHELL_SANITIZE into a for-Libtool-only wrapper.
* lib/m4sugar/m4sh.m4 (_AS_DETECT_REQUIRED, _AS_DETECT_SUGGESTED): Remove
m4_require of _AS_DETECT_BETTER_SHELL.
(_AS_CLEANUP): Add it here.
(_AS_DETECT_BETTER_SHELL): Just expand the test instead of appending it
to _AS_CLEANUP.
(_AS_SHELL_SANITIZE): New name of the old AS_SHELL_SANITIZE macro.
(AS_SHELL_SANITIZE): New macro hacking around Libtool misuse.
(AS_PREPARE): Use _AS_SHELL_SANITIZE.
(AS_INIT): Add m4_provide of itself.
commit cde022163b2e104f23c7ea70288fc9136fe2b765
Author: Paolo Bonzini <address@hidden>
Date: Wed Oct 15 15:59:42 2008 +0200
Use "test x$foo = xyes" to avoid upsetting Libtool's sh.test.
* lib/m4sugar/m4sh.m4 (_AS_DETECT_BETTER_SHELL, _AS_SHELL_FN_WORK): Use
"test x$foo = xyes".
-----------------------------------------------------------------------
Summary of changes:
ChangeLog | 53 +++++++++
NEWS | 3 +
doc/autoconf.texi | 276 ++++++++++++++++++++++++++++------------------
lib/autoconf/general.m4 | 2 +-
lib/autoconf/programs.m4 | 2 +-
lib/m4sugar/m4sh.m4 | 112 +++++++++++--------
6 files changed, 293 insertions(+), 155 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index 7cbb670..9789f57 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,58 @@
2008-10-15 Paolo Bonzini <address@hidden>
+ Updates to shell portability documentation.
+ * doc/autoconf.texi: Updates all references to "Portable Shell" and
+ "Limitations of Builtins" to use three-argument commands.
+ (Programming in M4sh): Document AS_ECHO, AS_ECHO_N, AS_UNSET.
+ (Portable Shell): Move here discussion about "Where is the POSIX
+ shell?" Mention that M4sh provides a SVR2 shell and takes care
+ of unsetting variables if necessary. Talk about M4sh and not only
+ Autoconf-generated scripts.
+ (Special Shell Variables): Talk about M4sh and not only
+ Autoconf-generated scripts. Don't talk about things that Autoconf
+ does not do. Mention problems of $LINENO with shell functions.
+ (Limitations of Builtins). Mention AS_ECHO and AS_ECHO_N. Move
+ discussion of eval bugs before discussion on proper use of eval.
+ Mention AS_IF. Reword why not to use "shift N". Mention "foo=;
+ unset foo" trick. Include M4sh code that unsets MAIL for Bash 2.01.
+ * NEWS: Update list of documented M4sh macros.
+
+2008-10-15 Paolo Bonzini <address@hidden>
+
+ Assume a (possibly buggy) `unset' is present after a
+ `better shell' was found.
+ * lib/autoconf/general.m4 (_AC_CACHE_DUMP): Use AS_UNSET.
+ * lib/autoconf/programs.m4 (AC_PROG_SED): Use AS_UNSET.
+ * lib/m4sugar/m4sh.m4 (_AS_UNSET_PREPARE): Provide $as_unset as an
+ alias for AS_UNSET, for backwards compatibility.
+ (_AS_DETECT_BETTER_SHELL): Set BASH_ENV and ENV to /dev/null in case
+ the shell does not support unset.
+ (_AS_SHELL_SANITIZE): Work around Bash 2.01 bugs. Unset BASH_ENV.
+ (AS_INIT, _AS_PREPARE, AS_PREPARE): Call it.
+ (AS_UNSET): Assume it is there but it might fail if the variable is
+ not set. Use it throughout instead of $as_unset.
+
+2008-10-15 Paolo Bonzini <address@hidden>
+
+ Turn AS_SHELL_SANITIZE into a for-Libtool-only wrapper.
+ * lib/m4sugar/m4sh.m4 (_AS_DETECT_REQUIRED, _AS_DETECT_SUGGESTED):
Remove
+ m4_require of _AS_DETECT_BETTER_SHELL.
+ (_AS_CLEANUP): Add it here.
+ (_AS_DETECT_BETTER_SHELL): Just expand the test instead of appending it
+ to _AS_CLEANUP.
+ (_AS_SHELL_SANITIZE): New name of the old AS_SHELL_SANITIZE macro.
+ (AS_SHELL_SANITIZE): New macro hacking around Libtool misuse.
+ (AS_PREPARE): Use _AS_SHELL_SANITIZE.
+ (AS_INIT): Add m4_provide of itself.
+
+2008-10-15 Paolo Bonzini <address@hidden>
+
+ Use "test x$foo = xyes" to avoid upsetting Libtool's sh.test.
+ * lib/m4sugar/m4sh.m4 (_AS_DETECT_BETTER_SHELL, _AS_SHELL_FN_WORK): Use
+ "test x$foo = xyes".
+
+2008-10-15 Paolo Bonzini <address@hidden>
+
Trim down the size of the better-shell test.
* lib/m4sugar/m4sh.at (_AT_DETECT_BETTER_SHELL): Store the common
snippets into shell variables.
diff --git a/NEWS b/NEWS
index 31e58c6..2f7914a 100644
--- a/NEWS
+++ b/NEWS
@@ -20,6 +20,9 @@ GNU Autoconf NEWS - User visible changes.
AS_ME_PREPARE
** The following m4sh macros are documented now:
+ AS_ECHO
+ AS_ECHO_N
+ AS_UNSET
AS_VERSION_COMPARE
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index ddd0638..fe51667 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -1030,9 +1030,10 @@ use. Autoconf macros already exist to check for many
features; see
you can use Autoconf template macros to produce custom checks; see
@ref{Writing Tests}, for information about them. For especially tricky
or specialized features, @file{configure.ac} might need to contain some
-hand-crafted shell commands; see @ref{Portable Shell}. The
address@hidden program can give you a good start in writing
address@hidden (@pxref{autoscan Invocation}, for more information).
+hand-crafted shell commands; see @ref{Portable Shell, , Portable Shell
+Programming}. The @command{autoscan} program can give you a good start
+in writing @file{configure.ac} (@pxref{autoscan Invocation}, for more
+information).
Previous versions of Autoconf promoted the name @file{configure.in},
which is somewhat ambiguous (the tool needed to process this file is not
@@ -11846,6 +11847,23 @@ if @code{$file} is @samp{/one/two/three}, the command
@end defmac
@end ignore
address@hidden AS_ECHO (@var{word})
address@hidden
+Emits @var{word} to the standard output, followed by a newline. @var{word}
+must be a single shell word (typically a quoted string). The bytes of
address@hidden are output as-is, even if it starts with "-" or contains "\".
+Redirections can be placed outside the macro invocation.
address@hidden defmac
+
address@hidden AS_ECHO_N (@var{word})
address@hidden
+Emits @var{word} to the standard output, without a following newline.
address@hidden must be a single shell word (typically a quoted string) and,
+for portability, should not include more than one newline. The bytes of
address@hidden are output as-is, even if it starts with "-" or contains "\".
+Redirections can be placed outside the macro invocation.
address@hidden defmac
+
@defmac AS_IF (@var{test1}, @ovar{run-if-true1}, @dots{}, @ovar{run-if-false})
@asindex{IF}
Run shell code @var{test1}. If @var{test1} exits with a zero status then
@@ -11911,6 +11929,12 @@ optimizing the common cases (@var{dir} or @var{file}
is @samp{.},
@var{file} is absolute, etc.).
@end defmac
address@hidden AS_UNSET (@var{var})
address@hidden
+Unsets the shell variable @var{var}, working around bugs in older
+shells (@pxref{Limitations of Builtins, , Limitations of Shell Builtins}).
address@hidden defmac
+
@defmac AS_VERSION_COMPARE (@var{version-1}, @var{version-2}, @
@ovar{action-if-less}, @ovar{action-if-equal}, @ovar{action-if-greater})
@asindex{VERSION_COMPARE}
@@ -12731,18 +12755,52 @@ test "$ac_cv_emxos2" = yes && EMXOS2=yes[]dnl
When writing your own checks, there are some shell-script programming
techniques you should avoid in order to make your code portable. The
Bourne shell and upward-compatible shells like the Korn shell and Bash
-have evolved over the years, but to prevent trouble, do not take
-advantage of features that were added after Unix version 7, circa
-1977 (@pxref{Systemology}).
+have evolved over the years, and many features added to the original
+System7 shell are now supported on all interesting porting targets.
+However, the following discussion between Russ Allbery and Robert Lipe
+is worth reading:
-You should not use aliases, negated character classes, or other features
-that are not found in all Bourne-compatible shells; restrict yourself
-to the lowest common denominator. Even @code{unset} is not supported
-by all shells!
address@hidden
+Russ Allbery:
-Shell functions are considered portable nowadays. However, some pitfalls
-have to be avoided for portable use of shell functions (@pxref{Shell
-Functions}).
address@hidden
+The @acronym{GNU} assumption that @command{/bin/sh} is the one and only shell
+leads to a permanent deadlock. Vendors don't want to break users'
+existing shell scripts, and there are some corner cases in the Bourne
+shell that are not completely compatible with a Posix shell. Thus,
+vendors who have taken this route will @emph{never} (address@hidden say
+never'') replace the Bourne shell (as @command{/bin/sh}) with a
+Posix shell.
address@hidden quotation
+
address@hidden
+Robert Lipe:
+
address@hidden
+This is exactly the problem. While most (at least most System V's) do
+have a Bourne shell that accepts shell functions most vendor
address@hidden/bin/sh} programs are not the Posix shell.
+
+So while most modern systems do have a shell @emph{somewhere} that meets the
+Posix standard, the challenge is to find it.
address@hidden quotation
+
+For this reason, part of the job of M4sh (@pxref{Programming in M4sh})
+is to find such a shell. But to prevent trouble, if you're not using
+M4sh you should not take advantage of features that were added after Unix
+version 7, circa 1977 (@pxref{Systemology}); you should not use aliases,
+negated character classes, or even @command{unset}. @code{#} comments,
+while not in Unix version 7, were retrofitted in the original Bourne
+shell and can be assumed to be part of the least common denominator.
+
+On the other hand, if you're using M4sh you can assume that the shell
+has the features that were added in SVR2, including shell functions,
address@hidden, @command{unset}, and I/O redirection for builtins. For
+more information, refer to @uref{http://@/www.in-ulm.de/@/~mascheck/@/bourne/}.
+However, some pitfalls have to be avoided for portable use of this
+constructs; these will be documented in the rest of this chapter.
+See in particular @ref{Shell Functions} and @ref{Limitations of
+Builtins, , Limitations of Shell Builtins}.
Some ancient systems have quite
small limits on the length of the @samp{#!} line; for instance, 32
@@ -12920,34 +12978,6 @@ The default Mac OS X @command{sh} was originally Zsh;
it was changed to
Bash in Mac OS X 10.2.
@end table
-The following discussion between Russ Allbery and Robert Lipe is worth
-reading:
-
address@hidden
-Russ Allbery:
-
address@hidden
-The @acronym{GNU} assumption that @command{/bin/sh} is the one and only shell
-leads to a permanent deadlock. Vendors don't want to break users'
-existing shell scripts, and there are some corner cases in the Bourne
-shell that are not completely compatible with a Posix shell. Thus,
-vendors who have taken this route will @emph{never} (address@hidden say
-never'') replace the Bourne shell (as @command{/bin/sh}) with a
-Posix shell.
address@hidden quotation
-
address@hidden
-Robert Lipe:
-
address@hidden
-This is exactly the problem. While most (at least most System V's) do
-have a Bourne shell that accepts shell functions most vendor
address@hidden/bin/sh} programs are not the Posix shell.
-
-So while most modern systems do have a shell @emph{somewhere} that meets the
-Posix standard, the challenge is to find it.
address@hidden quotation
-
@node Here-Documents
@section Here-Documents
@cindex Here-documents
@@ -13249,7 +13279,8 @@ esac
@noindent
Make sure you quote the brackets if appropriate and keep the backslash as
-first character (@pxref{Limitations of Builtins}).
+first character (@pxref{Limitations of Builtins, , Limitations of Shell
+Builtins}).
Also, because the colon is used as part of a drivespec, these systems don't
use it as path separator. When creating or accessing paths, you can use the
@@ -13891,9 +13922,10 @@ it's not worth worrying about working around these
horrendous bugs.
Some shell variables should not be used, since they can have a deep
influence on the behavior of the shell. In order to recover a sane
-behavior from the shell, some variables should be unset, but
address@hidden is not portable (@pxref{Limitations of Builtins}) and a
-fallback value is needed.
+behavior from the shell, some variables should be unset; M4sh takes
+care of this and provides fallback values, whenever needed, to cater
+for a very old @file{/bin/sh} that does not support @command{unset}.
+(@pxref{Portable Shell, , Portable Shell Programming}).
As a general rule, shell variable names containing a lower-case letter
are safe; you can define and use these variables without worrying about
@@ -13940,7 +13972,7 @@ In practice the shells that have this problem also
support
You can also avoid output by ensuring that your directory name is
absolute or anchored at @samp{./}, as in @samp{abs=`cd ./src && pwd`}.
-Autoconf-generated scripts automatically unset @env{CDPATH} if
+Configure scripts use M4sh, which automatically unsets @env{CDPATH} if
possible, so you need not worry about this problem in those scripts.
@item DUALCASE
@@ -13966,7 +13998,8 @@ supposed to affect only interactive shells. However,
at least one
shell (the pre-3.0 @sc{uwin} Korn shell) gets confused about
whether it is interactive, which means that (for example) a @env{PS1}
with a side effect can unexpectedly modify @samp{$?}. To work around
-this bug, Autoconf-generated scripts do something like this:
+this bug, M4sh scripts (including @file{configure} scripts) do something
+like this:
@example
(unset ENV) >/dev/null 2>&1 && unset ENV MAIL MAILPATH
@@ -13975,6 +14008,10 @@ PS2='> '
PS4='+ '
@end example
address@hidden
+(actually, there is some complication due to bugs in @command{unset};
+see @pxref{Limitations of Builtins, , Limitations of Shell Builtins}).
+
@item FPATH
The Korn shell uses @env{FPATH} to find shell functions, so avoid
@env{FPATH} in portable scripts. @env{FPATH} is consulted after
@@ -14017,20 +14054,23 @@ to this and join with a space anyway.
@evindex LC_NUMERIC
@evindex LC_TIME
-Autoconf-generated scripts normally set all these variables to
address@hidden because so much configuration code assumes the C locale and
-Posix requires that locale environment variables be set to
address@hidden if the C locale is desired. However, some older, nonstandard
-systems (notably @acronym{SCO}) break if locale environment variables
-are set to @samp{C}, so when running on these systems
-Autoconf-generated scripts unset the variables instead.
+You should set all these variables to @samp{C} because so much
+configuration code assumes the C locale and Posix requires that locale
+environment variables be set to @samp{C} if the C locale is desired;
address@hidden scripts and M4sh do that for you.
+Export these variables after setting them.
+
address@hidden However, some older, nonstandard
address@hidden systems (notably @acronym{SCO}) break if locale environment
variables
address@hidden are set to @samp{C}, so when running on these systems
address@hidden Autoconf-generated scripts unset the variables instead.
@item LANGUAGE
@evindex LANGUAGE
@env{LANGUAGE} is not specified by Posix, but it is a @acronym{GNU}
-extension that overrides @env{LC_ALL} in some cases, so
-Autoconf-generated scripts set it too.
+extension that overrides @env{LC_ALL} in some cases, so you (or M4sh)
+should set it too.
@item LC_ADDRESS
@itemx LC_IDENTIFICATION
@@ -14060,13 +14100,13 @@ character) with the line's number. In M4sh scripts
you should execute
@code{AS_LINENO_PREPARE} so that these workarounds are included in
your script; configure scripts do this automatically in @code{AC_INIT}.
-You should not rely on @code{LINENO} within @command{eval}, as the
-behavior differs in practice. Also, the possibility of the Sed
-prepass means that you should not rely on @code{$LINENO} when quoted,
-when in here-documents, or when in long commands that cross line
-boundaries. Subshells should be OK, though. In the following
-example, lines 1, 6, and 9 are portable, but the other instances of
address@hidden are not:
+You should not rely on @code{LINENO} within @command{eval} or shell
+functions, as the behavior differs in practice. Also, the possibility
+of the Sed prepass means that you should not rely on @code{$LINENO} when
+quoted, when in here-documents, or when in long commands that cross line
+boundaries. Subshells should be OK, though. In the following example,
+lines 1, 6, and 9 are portable, but the other instances of @code{LINENO}
+are not:
@example
@group
@@ -14187,7 +14227,7 @@ hence read-only. Do not use it.
@cindex Shell Functions
Nowadays, it is difficult to find a shell that does not support
-shell functions at all. However, some differences should be expected:
+shell functions at all. However, some differences should be expected.
Inside a shell function, you should not rely on the error status of a
subshell if the last command of that subshell was @code{exit} or
@@ -14260,10 +14300,11 @@ No, no, we are serious: some shells do have
limitations! :)
You should always keep in mind that any builtin or command may support
options, and therefore differ in behavior with arguments
-starting with a dash. For instance, the innocent @samp{echo "$word"}
+starting with a dash. For instance, even the innocent @samp{echo "$word"}
can give unexpected results when @code{word} starts with a dash. It is
often possible to avoid this problem using @samp{echo "x$word"}, taking
-the @samp{x} into account later in the pipe.
+the @samp{x} into account later in the pipe. Many of these limitations
+can be worked around using M4sh (@pxref{Programming in M4sh}).
@table @asis
@item @command{.}
@@ -14491,12 +14532,8 @@ Also please see the discussion of the @command{pwd}
command.
@prindex @command{echo}
The simple @command{echo} is probably the most surprising source of
portability troubles. It is not possible to use @samp{echo} portably
-unless both options and escape sequences are omitted. New applications
-which are not aiming at portability should use @samp{printf} instead of
address@hidden
-
-Don't expect any option. @xref{Preset Output Variables}, @code{ECHO_N}
-etc.@: for a means to simulate @option{-n}.
+unless both options and escape sequences are omitted. Don't expect any
+option.
Do not use backslashes in the arguments, as there is no consensus on
their handling. For @samp{echo '\n' | wc -l}, the @command{sh} of
@@ -14517,6 +14554,12 @@ $foo
EOF
@end example
+New applications which are not aiming at portability should use
address@hidden instead of @samp{echo}. M4sh provides the @code{AS_ECHO}
+and @code{AS_ECHO_N} macros (corresponding to @samp{echo -n} which use
address@hidden if it is available, or otherwise resort to various creative
+tricks in order to work around the above problems.
+
@item @command{eval}
@c -----------------
@@ -14524,9 +14567,27 @@ EOF
The @command{eval} command is useful in limited circumstances, e.g.,
using commands like @samp{eval table_$key=\$value} and @samp{eval
value=table_$key} to simulate a hash table when the key is known to be
-alphanumeric. However, @command{eval} is tricky to use on arbitrary
-arguments, even when it is implemented correctly.
+alphanumeric.
+
+You should also be wary of common bugs in @command{eval} implementations.
+In some shell implementations (e.g., older @command{ash}, address@hidden 3.8
address@hidden, @command{pdksh} v5.2.14 99/07/13.2, and @command{zsh}
+4.2.5), the arguments of @samp{eval} are evaluated in a context where
address@hidden is 0, so they exhibit behavior like this:
+
address@hidden
+$ @kbd{false; eval 'echo $?'}
+0
address@hidden example
+
+The correct behavior here is to output a nonzero value,
+but portable scripts should not rely on this.
+
+You should not rely on @code{LINENO} within @command{eval}.
address@hidden Shell Variables}.
+Note that, even though these bugs are easily avoided,
address@hidden is tricky to use on arbitrary arguments.
It is obviously unwise to use @samp{eval $cmd} if the string value of
@samp{cmd} was derived from an untrustworthy source. But even if the
string value is valid, @samp{eval $cmd} might not work as intended,
@@ -14550,23 +14611,6 @@ since it mistakenly replaces the contents of
@file{bar} by the
string @samp{cat foo}. No simple, general, and portable solution to
this problem is known.
-You should also be wary of common bugs in @command{eval} implementations.
-In some shell implementations (e.g., older @command{ash}, address@hidden 3.8
address@hidden, @command{pdksh} v5.2.14 99/07/13.2, and @command{zsh}
-4.2.5), the arguments of @samp{eval} are evaluated in a context where
address@hidden is 0, so they exhibit behavior like this:
-
address@hidden
-$ @kbd{false; eval 'echo $?'}
-0
address@hidden example
-
-The correct behavior here is to output a nonzero value,
-but portable scripts should not rely on this.
-
-You should not rely on @code{LINENO} within @command{eval}.
address@hidden Shell Variables}.
-
@item @command{exec}
@c -----------------
@prindex @command{exec}
@@ -14752,6 +14796,18 @@ if cmp -s file file.new; then :; else
fi
@end example
address@hidden
+Or, especially if the @dfn{else} branch is short, you can use @code{||}.
+In M4sh, the @code{AS_IF} macro provides an easy way to write these kinds
+of conditionals as;
+
address@hidden
+AS_IF([cmp -s file file.new], [], [mv file.new file])
address@hidden example
+
+This is especially useful in other M4 macros, where the @dfn{then} and
address@hidden branches might be macro arguments.
+
There are shells that do not reset the exit status from an @command{if}:
@example
@@ -14917,8 +14973,8 @@ Not only is @command{shift}ing a bad idea when there is
nothing left to
shift, but in addition it is not portable: the shell of @acronym{MIPS
RISC/OS} 4.52 refuses to do it.
-Don't use @samp{shift 2} etc.; it was not in the 7th Edition Bourne shell,
-and it is also absent in many pre-Posix shells.
+Don't use @samp{shift 2} etc.; while it in the SVR1 shell (1983),
+it is also absent in many pre-Posix shells.
@item @command{source}
@@ -15115,23 +15171,29 @@ for @command{true}.
@c ------------------
@prindex @command{unset}
In some nonconforming shells (e.g., Bash 2.05a), @code{unset FOO} fails
-when @code{FOO} is not set. Also, Bash 2.01 mishandles @code{unset
-MAIL} in some cases and dumps core.
+when @code{FOO} is not set. You can use
+
address@hidden
+FOO=; unset FOO
address@hidden smallexample
+
+if you are not sure that @code{FOO} is set.
-A few ancient shells lack @command{unset} entirely. Nevertheless, because
-it is extremely useful to disable embarrassing variables such as
address@hidden, you can test for its existence and use
-it @emph{provided} you give a neutralizing value when @command{unset} is
-not supported:
+A few ancient shells lack @command{unset} entirely. For some variables
+such as @code{PS1}, you can use a neutralizing value instead:
@smallexample
-# "|| exit" suppresses any "Segmentation fault" message.
-if ( (MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
- unset=unset
-else
- unset=false
-fi
-$unset PS1 || PS1='$ '
+PS1='$ '
address@hidden smallexample
+
+Usually, shells that do not support @command{unset} need less effort to
+make the environment sane, so for example is not a problem if you cannot
+unset @command{CDPATH} on those shells. However, Bash 2.01 mishandles
address@hidden MAIL} in some cases and dumps core. So, you should do
+something like
+
address@hidden
+( (unset MAIL) || exit 1) >/dev/null 2>&1 && unset MAIL || :
@end smallexample
@noindent
diff --git a/lib/autoconf/general.m4 b/lib/autoconf/general.m4
index 986b7af..beb3104 100644
--- a/lib/autoconf/general.m4
+++ b/lib/autoconf/general.m4
@@ -1894,7 +1894,7 @@ m4_define([_AC_CACHE_DUMP],
case $ac_var in #(
_ | IFS | as_nl) ;; #(
BASH_ARGV | BASH_SOURCE) eval $ac_var= ;; #(
- *) $as_unset $ac_var ;;
+ *) AS_UNSET([$ac_var]) ;;
esac ;;
esac
done
diff --git a/lib/autoconf/programs.m4 b/lib/autoconf/programs.m4
index 63f8a13..45a74b5 100644
--- a/lib/autoconf/programs.m4
+++ b/lib/autoconf/programs.m4
@@ -894,7 +894,7 @@ AC_DEFUN([AC_PROG_SED],
ac_script="$ac_script$as_nl$ac_script"
done
echo "$ac_script" 2>/dev/null | sed 99q >conftest.sed
- $as_unset ac_script || ac_script=
+ AS_UNSET([ac_script])
_AC_PATH_PROGS_FEATURE_CHECK(SED, [sed gsed],
[_AC_FEATURE_CHECK_LENGTH([ac_path_SED], [ac_cv_path_SED],
["$ac_path_SED" -f conftest.sed])])])
diff --git a/lib/m4sugar/m4sh.m4 b/lib/m4sugar/m4sh.m4
index 20b5772..64cc8db 100644
--- a/lib/m4sugar/m4sh.m4
+++ b/lib/m4sugar/m4sh.m4
@@ -138,7 +138,8 @@ m4_define([_AS_BOURNE_COMPATIBLE],
# -----------
# Expanded as the last thing before m4sugar cleanup begins. Macros
# may append m4sh cleanup hooks to this as appropriate.
-m4_define([_AS_CLEANUP])
+m4_define([_AS_CLEANUP],
+[m4_divert_text([M4SH-SANITIZE], [_AS_DETECT_BETTER_SHELL])])
# AS_COPYRIGHT(TEXT)
@@ -155,9 +156,9 @@ $1], [^], address@hidden:@ ])])])
# _AS_DETECT_REQUIRED(TEST)
# -------------------------
# Refuse to execute under a shell that does not pass the given TEST.
+# Does not do AS_REQUIRE for the better-shell detection code.
m4_defun([_AS_DETECT_REQUIRED],
-[m4_require([_AS_DETECT_BETTER_SHELL])dnl
-m4_set_add([_AS_DETECT_REQUIRED_BODY],
+[m4_set_add([_AS_DETECT_REQUIRED_BODY],
[($1) || AS_EXIT(1)
])])
@@ -165,9 +166,9 @@ m4_set_add([_AS_DETECT_REQUIRED_BODY],
# _AS_DETECT_SUGGESTED(TEST)
# --------------------------
# Prefer to execute under a shell that passes the given TEST.
+# Does not do AS_REQUIRE for the better-shell detection code.
m4_defun([_AS_DETECT_SUGGESTED],
-[m4_require([_AS_DETECT_BETTER_SHELL])dnl
-m4_set_add([_AS_DETECT_SUGGESTED_BODY],
+[m4_set_add([_AS_DETECT_SUGGESTED_BODY],
[($1) || AS_EXIT(1)
])])
@@ -186,10 +187,8 @@ m4_set_add([_AS_DETECT_SUGGESTED_BODY],
# FIXME: The code should test for the OSF bug described in
# <http://lists.gnu.org/archive/html/autoconf-patches/2006-03/msg00081.html>.
#
-m4_defun_once([_AS_DETECT_BETTER_SHELL],
-[AS_REQUIRE([_AS_UNSET_PREPARE], , [M4SH-SANITIZE])dnl
-m4_append([_AS_CLEANUP], [m4_divert_text([M4SH-SANITIZE], [
-if test "x$CONFIG_SHELL" = x; then
+m4_defun([_AS_DETECT_BETTER_SHELL],
+[if test "x$CONFIG_SHELL" = x; then
dnl Remove any tests from suggested that are also required
m4_set_foreach([_AS_DETECT_SUGGESTED_BODY], [AS_snippet],
[m4_set_contains([_AS_DETECT_REQUIRED_BODY],
@@ -203,7 +202,7 @@ dnl Remove any tests from suggested that are also required
AS_IF([_AS_RUN(["$as_required"])],
[as_have_required=yes],
[as_have_required=no])])
- AS_IF([test $as_have_required = yes && _AS_RUN(["$as_suggested"])],
+ AS_IF([test x$as_have_required = xyes && _AS_RUN(["$as_suggested"])],
[],
[as_candidate_shells=
_AS_PATH_WALK([/bin$PATH_SEPARATOR/usr/bin$PATH_SEPARATOR$PATH],
@@ -225,13 +224,16 @@ dnl Remove any tests from suggested that are also required
done
AS_IF([test "x$CONFIG_SHELL" != x],
- [for as_var in BASH_ENV ENV
- do ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
- done
+ [# We cannot yet assume a decent shell, so we have to provide a
+ # neutralization value for shells without unset; and this also
+ # works around shells that cannot unset nonexistent variables.
+ BASH_ENV=/dev/null
+ ENV=/dev/null
+ (unset BASH_ENV) >/dev/null 2>&1 && unset BASH_ENV ENV
export CONFIG_SHELL
exec "$CONFIG_SHELL" "$as_myself" ${1+"address@hidden"}])
- AS_IF([test $as_have_required = no],
+ AS_IF([test x$as_have_required = xno],
[echo This script requires a shell more modern than all the
echo shells that I found on your system. Please install a
echo modern shell, or manually run the script under such a
@@ -239,7 +241,7 @@ dnl Remove any tests from suggested that are also required
AS_EXIT(1)])
])
fi
-])])])# _AS_DETECT_BETTER_SHELL
+])# _AS_DETECT_BETTER_SHELL
# _AS_PREPARE
@@ -271,6 +273,7 @@ _AS_MKDIR_P_PREPARE
_AS_TEST_PREPARE
_AS_TR_CPP_PREPARE
_AS_TR_SH_PREPARE
+_AS_UNSET_PREPARE
])
# AS_PREPARE
@@ -291,6 +294,7 @@ AS_REQUIRE([_AS_MKDIR_P_PREPARE])
AS_REQUIRE([_AS_TEST_PREPARE])
AS_REQUIRE([_AS_TR_CPP_PREPARE])
AS_REQUIRE([_AS_TR_SH_PREPARE])
+AS_REQUIRE([_AS_UNSET_PREPARE])
])
@@ -316,8 +320,7 @@ m4_if(m4_eval(_m4_divert(_m4_divert_dump) <=
_m4_divert(_m4_divert_desired)), 1,
# xx_REQUIRE macros, BODY-TO-EXPAND is mandatory.
#
m4_define([AS_REQUIRE_SHELL_FN],
-[_AS_DETECT_REQUIRED([_AS_SHELL_FN_WORK])dnl
-AS_REQUIRE([AS_SHELL_FN_$1], [m4_provide([AS_SHELL_FN_$1])$1 ()
+[AS_REQUIRE([AS_SHELL_FN_$1], [m4_provide([AS_SHELL_FN_$1])$1 ()
{
$2
}], m4_default_quoted([$3], [M4SH-INIT-FN]))])
@@ -374,13 +377,14 @@ AS_IF([as_func_ret_failure],
AS_IF([( set x; as_func_ret_success y && test x = "[$]1" )], [],
[exitcode=1
echo positional parameters were not saved.])
-test $exitcode = 0[]dnl
+test x$exitcode = x0[]dnl
])# _AS_SHELL_FN_WORK
-# AS_SHELL_SANITIZE
-# -----------------
-m4_defun([AS_SHELL_SANITIZE],
+# _AS_SHELL_SANITIZE
+# ------------------
+# This is the prolog that is emitted by AS_INIT and AS_INIT_GENERATED.
+m4_defun([_AS_SHELL_SANITIZE],
[## --------------------- ##
## M4sh Initialization. ##
## --------------------- ##
@@ -391,7 +395,6 @@ AS_BOURNE_COMPATIBLE
_AS_CR_PREPARE
_AS_ECHO_PREPARE
_AS_PATH_SEPARATOR_PREPARE
-_AS_UNSET_PREPARE
# IFS
# We need space, tab and new line, in precisely that order. Quoting is
@@ -417,9 +420,12 @@ if test ! -f "$as_myself"; then
AS_EXIT
fi
-# Work around bugs in pre-3.0 UWIN ksh.
-for as_var in ENV MAIL MAILPATH
-do ($as_unset $as_var) >/dev/null 2>&1 && $as_unset $as_var
+# Unset variables that we do not need and cause bugs (e.g. in pre-3.0 UWIN
ksh).
+# But do not cause bugs in bash 2.01; the "|| exit 1" suppresses any
+# "Segmentation fault" message there. '((' could trigger a bug in pdksh
5.2.14.
+for as_var in BASH_ENV ENV MAIL MAILPATH
+do eval test x\${$as_var+set} = xset && dnl
+ ( (unset $as_var) || exit 1) >/dev/null 2>&1 && unset $as_var || :
done
PS1='$ '
PS2='> '
@@ -432,8 +438,22 @@ LANGUAGE=C
export LANGUAGE
# CDPATH.
-$as_unset CDPATH
-])# AS_SHELL_SANITIZE
+(unset CDPATH) >/dev/null 2>&1 && unset CDPATH
+])# _AS_SHELL_SANITIZE
+
+
+# AS_SHELL_SANITIZE
+# -----------------
+# This is only needed for the sake of Libtool, which screws up royally
+# in its usage of M4sh internals.
+m4_define([AS_SHELL_SANITIZE],
+[_AS_SHELL_SANITIZE
+m4_provide_if([AS_INIT], [],
+[m4_provide([AS_INIT])
+_AS_DETECT_REQUIRED([_AS_SHELL_FN_WORK])
+_AS_DETECT_BETTER_SHELL
+_AS_UNSET_PREPARE
+])])
## ----------------------------- ##
@@ -513,27 +533,24 @@ 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.
-# Avoid 'if ((', as that triggers a bug in pdksh 5.2.14.
+# Define $as_unset to execute AS_UNSET, for backwards compatibility
+# with older versions of M4sh.
m4_defun([_AS_UNSET_PREPARE],
-[# Support unset when possible.
-if ( (MAIL=60; unset MAIL) || exit) >/dev/null 2>&1; then
- as_unset=unset
-else
- as_unset=false
-fi
+[as_func_unset ()
+{
+ AS_UNSET([$[1]])
+}
+as_unset=as_func_unset
])
-# AS_UNSET(VAR, [VALUE-IF-UNSET-NOT-SUPPORTED = `'])
-# --------------------------------------------------
-# Try to unset the env VAR, otherwise set it to
-# VALUE-IF-UNSET-NOT-SUPPORTED. `as_unset' must have been computed.
+# AS_UNSET(VAR)
+# -------------
+# Unset the env VAR, working around shells that do not allow unsetting
+# a variable that is not already set. You should not unset MAIL and
+# MAILCHECK, as that triggers a bug in Bash 2.01.
m4_defun([AS_UNSET],
-[AS_REQUIRE([_AS_UNSET_PREPARE])dnl
-$as_unset $1 || test "${$1+set}" != set || { $1=$2; export $1; }])
+[{ AS_LITERAL_IF([$1], [], [eval ])$1=; unset $1;}])
@@ -934,7 +951,7 @@ m4_defun([AS_LINENO_PREPARE], [AS_REQUIRE([_$0])])
m4_defun([_AS_LINENO_PREPARE],
[AS_REQUIRE([_AS_CR_PREPARE])dnl
AS_REQUIRE([_AS_ME_PREPARE])dnl
-_AS_DETECT_SUGGESTED([_AS_LINENO_WORKS])
+_AS_DETECT_SUGGESTED([_AS_LINENO_WORKS])dnl
_AS_LINENO_WORKS || {
dnl Create $as_me.lineno as a copy of $as_myself, but with $LINENO
@@ -1683,7 +1700,7 @@ m4_define([AS_VAR_POPDEF],
# for more detail.
m4_defun([AS_INIT_GENERATED],
[m4_require([AS_PREPARE])dnl
-AS_SHELL_SANITIZE
+_AS_SHELL_SANITIZE
_AS_PREPARE])
# AS_INIT
@@ -1693,6 +1710,7 @@ m4_define([AS_INIT],
[# Wrap our cleanup prior to m4sugar's cleanup.
m4_wrap([_AS_CLEANUP])
m4_init
+m4_provide([AS_INIT])
# Forbidden tokens and exceptions.
m4_pattern_forbid([^_?AS_])
@@ -1701,9 +1719,11 @@ m4_pattern_forbid([^_?AS_])
m4_divert_text([BINSH], address@hidden:@! /bin/sh])
m4_divert_text([HEADER-COMMENT],
address@hidden:@ Generated from __file__ by m4_PACKAGE_STRING.])
-m4_divert_text([M4SH-SANITIZE], [AS_SHELL_SANITIZE])
+m4_divert_text([M4SH-SANITIZE], [_AS_SHELL_SANITIZE])
# Let's go!
m4_divert_pop([KILL])[]dnl
m4_divert_push([BODY])[]dnl
+_AS_DETECT_REQUIRED([_AS_SHELL_FN_WORK])dnl
+AS_REQUIRE([_AS_UNSET_PREPARE])dnl For backwards compatibility.
])
hooks/post-receive
--
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