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Document shell function environment pitfall.

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* doc/autoconf.texi (Shell Functions): Document bugs in bash,
Solaris /bin/sh.

Signed-off-by: Eric Blake <ebb9@byu.net>
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Eric Blake 2008-10-14 11:26:58 -06:00
parent 920874ceda
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@ -1,3 +1,9 @@
2008-10-14 Eric Blake <ebb9@byu.net>
Document shell function environment pitfall.
* doc/autoconf.texi (Shell Functions): Document bugs in bash,
Solaris /bin/sh.
2008-10-14 Paolo Bonzini <bonzini@gnu.org>
Use m4_require to implement AS_REQUIRE.

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doc/autoconf.texi
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@ -14225,6 +14225,23 @@ For example, Korn shells reset and restore trace output (@samp{set -x})
and other options upon function entry and exit. Inside a function,
@acronym{IRIX} sh sets @samp{$0} to the function name.
It is not portable to pass temporary environment variables to shell
functions. Solaris @command{/bin/sh} does not see the variable. Meanwhile,
@command{bash} 3.2 breaks the Posix rule that the assignment must not affect
the current environment, but only when Posix compliance is requested!
@example
$ @kbd{/bin/sh -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}
@result{}
$ @kbd{bash -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}1
@result{}
$ @kbd{bash -c 'set -o posix; func()@{ echo $a;@}; a=1 func; echo $a'}
@result{}1
@result{}1
@end example
Some ancient Bourne shell variants with function support did not reset
@samp{$@var{i}, @var{i} >= 0}, upon function exit, so effectively the
arguments of the script were lost after the first function invocation.