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Port to AIX 7.2 ksh93
Problem reported in <https://savannah.gnu.org/support/?111102>. * lib/autotest/general.m4: * lib/m4sugar/m4sh.m4 (_AS_REEXEC_WITH_SHELL): * tests/wrapper.as: Port to AIX 7.2 ksh93, whidh mishandles ${1+"$@"}, by not using that construct.
This commit is contained in:
Paul Eggert
parent
226267d60b
commit
e1c7713496
3
NEWS
3
NEWS
@ -35,6 +35,9 @@ GNU Autoconf NEWS - User visible changes.
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*** AC_PROG_OBJC now finds the GNU Objective-C compiler, as packaged in
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EPEL 9, by default, without the user having to set the OBJC variable.
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*** Autoconf no longer generates ${1+"$@"} in scripts, working around
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a bug in AIX 7.2 ksh93.
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* Noteworthy changes in release 2.72 (2023-12-22) [release]
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** Backward incompatibilities
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@ -15302,9 +15302,7 @@ breaking the bracket-matching highlighting from Emacsen. Note the
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preferred style to escape from M4: @samp{$[1]}, @samp{$[@@]}, etc. Do
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not escape when it is unnecessary. Common examples of useless quotation
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are @samp{[$]$1} (write @samp{$$1}), @samp{[$]var} (use @samp{$var}),
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etc. If you add portability issues to the picture, you'll prefer
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@samp{$@{1+"$[@@]"@}} to @samp{"[$]@@"}, and you'll prefer do something
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better than hacking Autoconf @code{:-)}.
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etc.
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When using @command{sed}, don't use @option{-e} except for indenting
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purposes. With the @code{s} and @code{y} commands, the preferred
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@ -15685,7 +15683,7 @@ set @code{NULLCMD} to @samp{:}. @xref{Compatibility, , Compatibility,
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zsh, The Z Shell Manual}, for details.
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The default Mac OS X @command{sh} was originally Zsh; it was changed to
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Bash in Mac OS X 10.2.
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Bash in Mac OS X 10.2 (2002) and changed back to Zsh in macOS 10.15 (2019).
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@end table
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@node Invoking the Shell
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@ -16460,17 +16458,37 @@ There are also portability pitfalls with particular expansions:
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@table @code
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@item $@@
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@cindex @code{"$@@"}
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One of the most famous shell-portability issues is related to
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@samp{"$@@"}. When there are no positional arguments, Posix says
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that @samp{"$@@"} is supposed to be equivalent to nothing, but the
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original Unix version 7 Bourne shell treated it as equivalent to
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@samp{""} instead, and this behavior survives in later implementations
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like Digital Unix 5.0.
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Autoconf macros often use the @command{set} command to update
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@samp{$@@}, so if you are writing shell code intended for
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@command{configure} you should not assume that the value of @samp{$@@}
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persists for any length of time.
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The traditional way to work around this portability problem is to use
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@samp{$@{1+"$@@"@}}. Unfortunately this method does not work with
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Zsh (3.x and 4.x), which is used on Mac OS X@. When emulating
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the Bourne shell, Zsh performs word splitting on @samp{$@{1+"$@@"@}}:
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You may see usages like @samp{$@{1+"$@@"@}} in older shell scripts
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designed to work around a portability problem in ancient shells.
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Unfortunately this runs afoul of bugs in more-recent shells, and
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nowadays it is better to use plain @samp{"$@@"} insteadl.
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The portability problem with ancient shells was significant.
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When there are no positional arguments @samp{"$@@"} should be discarded,
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but the original Unix version 7 Bourne shell mistakenly treated it as
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equivalent to @samp{""} instead, and many ancient shells followed its lead.
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For many years shell scripts worked around this portability problem by
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using @samp{$@{1+"$@@"@}} instead of @samp{"$@@"}, and you may see this
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usage in older scripts. Unfortunately, @samp{$@{1+"$@@"@}} does not
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work with @command{ksh93} M 93t+ (2009) as shipped in AIX 7.2 (2015),
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as this shell drops trailing arguments:
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@example
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$ @kbd{set a b c ""}
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$ @kbd{set $@{1+"$@@"@}}
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$ @kbd{echo $#}
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3
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@end example
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Also, @samp{$@{1+"$@@"@}} does not work with Zsh 4.2.6 (2005) and
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earlier, as shipped in Mac OS X releases before 10.5, as this old Zsh
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incorrectly word splits the result:
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@example
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zsh $ @kbd{emulate sh}
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@ -16483,42 +16501,40 @@ World
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!
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@end example
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To work around these problems Autoconf does two things. First, in the
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shell code that it generates Autoconf avoids @samp{"$@@"} if it is
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possible that there may be no positional arguments. You can use this
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workaround in your own code, too, if you want it to be portable to
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ancient shells. For example, instead of:
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@example
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cat conftest.c "$@@"
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@end example
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you can use this:
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@example
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case $# in
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0) cat conftest.c;;
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*) cat conftest.c "$@@";;
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esac
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@end example
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@noindent
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Zsh handles plain @samp{"$@@"} properly, but we can't use plain
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@samp{"$@@"} because of the portability problems mentioned above.
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One workaround relies on Zsh's ``global aliases'' to convert
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Second, Autoconf-generated @command{configure} scripts work around most
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of the old Zsh problem by using Zsh's ``global aliases'' to convert
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@samp{$@{1+"$@@"@}} into @samp{"$@@"} by itself:
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@example
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test $@{ZSH_VERSION+y@} && alias -g '$@{1+"$@@"@}'='"$@@"'
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@end example
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Zsh only recognizes this alias when a shell word matches it exactly;
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@samp{"foo"$@{1+"$@@"@}} remains subject to word splitting. Since this
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case always yields at least one shell word, use plain @samp{"$@@"}.
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A more conservative workaround is to avoid @samp{"$@@"} if it is
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possible that there may be no positional arguments. For example,
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instead of:
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@example
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cat conftest.c "$@@"
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@end example
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you can use this instead:
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@example
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case $# in
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0) cat conftest.c;;
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*) cat conftest.c "$@@";;
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esac
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@end example
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Autoconf macros often use the @command{set} command to update
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@samp{$@@}, so if you are writing shell code intended for
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@command{configure} you should not assume that the value of @samp{$@@}
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persists for any length of time.
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This workaround is for the benefit of any instances of
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@samp{$@{1+"$@@"@}} in user-written code appearing in
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@command{configure} scripts. However, it is not a complete solution, as
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Zsh recognizes the alias only when a shell word matches it exactly,
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which means older Zsh still mishandles more-complicated cases like
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@samp{"foo"$@{1+"$@@"@}}.
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@item $@{10@}
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@cindex positional parameters
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@ -18317,20 +18333,14 @@ for arg; do
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done
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@end example
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If you want to explicitly refer to the positional arguments, given the
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@samp{$@@} bug (@pxref{Shell Substitutions}), use:
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If you want to explicitly refer to the positional arguments, use:
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@example
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for arg in $@{1+"$@@"@}; do
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for arg in "$@@"; do
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echo "$arg"
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done
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@end example
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@noindent
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But keep in mind that Zsh, even in Bourne shell emulation mode, performs
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word splitting on @samp{$@{1+"$@@"@}}; see @ref{Shell Substitutions},
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item @samp{$@@}, for more.
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Posix requires support for a @command{for} loop with no list after
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@code{in}. However, Solaris 10 @command{/bin/sh} treats that as a syntax
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error. It is possible to work around this by providing any shell word
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@ -19730,7 +19740,7 @@ was equivalent to @samp{sources='*.c not found'} in the absence of
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The behavior of @command{ls} on a directory that is being concurrently
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modified is not always predictable, because of a data race where cached
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information returned by @code{readdir} does not match the current
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directory state. In fact, MacOS 10.5 has an intermittent bug where
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directory state. In fact, Mac OS X 10.5 had an intermittent bug where
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@code{readdir}, and thus @command{ls}, sometimes lists a file more than
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once if other files were added or removed from the directory immediately
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prior to the @command{ls} call. Since @command{ls} already sorts its
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@ -19856,7 +19866,7 @@ perfectly portable among Posix hosts.
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@c ---------------
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@prindex @command{od}
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In MacOS X versions prior to 10.4.3, @command{od} does not support the
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In Mac OS X versions prior to 10.4.3, @command{od} does not support the
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standard Posix options @option{-A}, @option{-j}, @option{-N}, or
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@option{-t}, or the XSI option, @option{-s}. The only
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supported Posix option is @option{-v}, and the only supported
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@ -19962,7 +19972,7 @@ than to rely on @samp{[A-Z]}.
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Additionally, Posix states that regular expressions are only
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well-defined on characters. Unfortunately, there exist platforms such
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as MacOS X 10.5 where not all 8-bit byte values are valid characters,
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as Mac OS X 10.5 where not all 8-bit byte values are valid characters,
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even though that platform has a single-byte @samp{C} locale. And Posix
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allows the existence of a multi-byte @samp{C} locale, although that does
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not yet appear to be a common implementation. At any rate, it means
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@ -20107,7 +20117,7 @@ should be followed by a newline. Otherwise some @command{sed}
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implementations (e.g., OpenBSD 3.9) do not append a newline to the
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inserted text.
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Many @command{sed} implementations (e.g., MacOS X 10.4,
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Many @command{sed} implementations (e.g., Mac OS X 10.4,
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OpenBSD 3.9, Solaris 10
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@command{/usr/ucb/sed}) strip leading white space from the text of
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@samp{a}, @samp{c}, and @samp{i} commands. Prepend a backslash to
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@ -359,7 +359,7 @@ same file).
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our %_directory_cache;
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sub dir_has_case_matching_file ($$)
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{
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# Note that print File::Spec->case_tolerant returns 0 even on MacOS
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# Note that print File::Spec->case_tolerant returns 0 even on Mac OS
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# X (with Perl v5.8.1-RC3 at least), so do not try to shortcut this
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# function using that.
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@ -378,11 +378,13 @@ at_fn_create_debugging_script ()
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{
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{
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echo "#! /bin/sh" &&
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echo 'test ${ZSH_VERSION+y} dnl
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&& alias -g '\''${1+"$[@]"}'\''='\''"$[@]"'\''' &&
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AS_ECHO(["cd '$at_dir'"]) &&
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AS_ECHO(["exec \${CONFIG_SHELL-$SHELL} \"$at_myself\" -v -d ]dnl
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[$at_debug_args $at_group \${1+\"\$[@]\"}"]) &&
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AS_ECHO(['case $[#] in']) &&
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AS_ECHO([" 0) exec \${CONFIG_SHELL-$SHELL} \"$at_myself\" -v -d ]dnl
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[$at_debug_args $at_group ;;"]) &&
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AS_ECHO([" *) exec \${CONFIG_SHELL-$SHELL} \"$at_myself\" -v -d ]dnl
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[$at_debug_args $at_group \"\$[@]\" ;;"]) &&
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AS_ECHO([esac]) &&
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echo 'exit 1'
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} >"$at_group_dir/run" &&
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chmod +x "$at_group_dir/run"
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@ -108,7 +108,7 @@ m4_define([_AS_BOURNE_COMPATIBLE],
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[emulate sh
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NULLCMD=:
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[#] Pre-4.2 versions of Zsh do word splitting on ${1+"$[@]"}, which
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# is contrary to our usage. Disable this feature.
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# contradicts POSIX and common usage. Disable this.
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alias -g '${1+"$[@]"}'='"$[@]"'
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setopt NO_GLOB_SUBST],
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[AS_CASE([`(set -o) 2>/dev/null`], [*posix*], [set -o posix])])
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@ -294,7 +294,10 @@ case $- in @%:@ ((((
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*x* ) as_opts=-x ;;
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* ) as_opts= ;;
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esac
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exec $1 $as_opts "$as_myself" ${1+"$[@]"}
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case [$]@%:@ in @%:@ ((
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0) exec $1 $as_opts "$as_myself" ;;
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*) exec $1 $as_opts "$as_myself" "$[@]" ;;
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esac
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# Admittedly, this is quite paranoid, since all the known shells bail
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# out after a failed 'exec'.
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AS_ECHO(["$[]0: could not re-execute with $1"]) >&2
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@ -23,7 +23,7 @@
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# that tests have the same side effects regardless of caching.
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#
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# The sed script duplicates uniq functionality (thanks to 'info sed
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# uniq' for the recipe), in order to avoid a MacOS 10.5 bug where
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# uniq' for the recipe), in order to avoid a Mac OS 10.5 bug where
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# readdir can list a file multiple times in a rapidly changing
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# directory, while avoiding yet another fork.
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m4_defun([AC_STATE_SAVE],
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@ -29,16 +29,15 @@ trailer_m4='@abs_top_srcdir@/lib/autoconf/trailer.m4'
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export AUTOCONF AUTOHEADER AUTOM4TE AUTOM4TE_CFG
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export autom4te_buildauxdir autom4te_perllibdir trailer_m4
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case '@wrap_program@' in
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ifnames)
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# Does not have lib files.
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exec '@abs_top_builddir@/bin/@wrap_program@' ${1+"$@"}
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;;
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*)
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# We might need files from the build tree (frozen files), in
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# addition of src files.
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exec '@abs_top_builddir@/bin/@wrap_program@' \
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-B '@abs_top_builddir@'/lib \
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-B '@abs_top_srcdir@'/lib ${1+"$@"}
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# Programs other than ifnames might need files from the build tree
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# (frozen files), in addition to src files.
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prog='@abs_top_builddir@/bin/@wrap_program@'
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buildlib='@abs_top_builddir@/lib'
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srclib='@abs_top_srcdir@/lib'
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case $#,'@wrap_program@' in
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0,ifnames) exec "$prog" ;;
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*,ifnames) exec "$prog" "$@" ;;
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0,*) exec "$prog" -B "$buildlib" -B "$srclib" ;;
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*) exec "$prog" -B "$buildlib" -B "$srclib" "$@" ;;
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esac
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exit 1
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