[SCM] GNU Autoconf source repository branch, master, updated. v2.67-11-g5adc15b

[Eric Blake]

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- Log -----------------------------------------------------------------
commit 5adc15b7b64622cf6f7f76e8b6f5cbde4be82851
Author: Eric Blake <address@hidden>
Date:   Tue Aug 3 15:56:07 2010 -0600

    docs: mention bash bug with word splitting
    
    * doc/autoconf.texi (Shell Substitutions): Document bash bug, and
    zsh default behavior difference.
    Reported by Ralf Wildenhues.

commit 608c89c8c6547885d571780852c9613f3948737f
Author: Eric Blake <address@hidden>
Date:   Tue Aug 3 15:40:16 2010 -0600

    docs: mention ksh bug with function syntax
    
    * doc/autoconf.texi (Shell Functions): Document ksh93 limitation.
    
    Signed-off-by: Eric Blake <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog         |   10 +++++++++
 doc/autoconf.texi |   54 ++++++++++++++++++++++++++++++++++++++++++++++------
 2 files changed, 57 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 2cbd690..7184742 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2010-08-03  Eric Blake  <address@hidden>
+
+       docs: mention bash bug with word splitting
+       * doc/autoconf.texi (Shell Substitutions): Document bash bug, and
+       zsh default behavior difference.
+       Reported by Ralf Wildenhues.
+
+       docs: mention ksh bug with function syntax
+       * doc/autoconf.texi (Shell Functions): Document ksh93 limitation.
+
 2010-08-03  Ralf Wildenhues  <address@hidden>
 
        Fix typo in Autotest color test, for dash testsuite failure.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index df0e298..b7e2c19 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -15283,6 +15283,32 @@ $ @kbd{echo "`echo \"hello\"`"}
 There is just no portable way to use double-quoted strings inside
 double-quoted back-quoted expressions (pfew!).
 
+Bash 4.1 has a bug where quoted empty strings adjacent to unquoted
+parameter expansions are elided during word splitting.  Meanwhile, zsh
+does not perform word splitting except when in Bourne compatibility
+mode.  In the example below, the correct behavior is to have five
+arguments to the function, and exactly two spaces on either side of the
+middle @samp{-}, since word splitting collapses multiple spaces in
address@hidden but leaves empty arguments intact.
+
address@hidden
+$ @kbd{bash -c 'n() @{ echo "$#$@@"; @}; f="  -  "; n - ""$f"" -'}
+3- - -
+$ @kbd{ksh -c 'n() @{ echo "$#$@@"; @}; f="  -  "; n - ""$f"" -'}
+5-  -  -
+$ @kbd{zsh -c 'n() @{ echo "$#$@@"; @}; f="  -  "; n - ""$f"" -'}
+3-   -   -
+$ @kbd{zsh -c 'emulate sh;}
+> @kbd{n() @{ echo "$#$@@"; @}; f="  -  "; n - ""$f"" -'}
+5-  -  -
address@hidden example
+
address@hidden
+You can work around this by doing manual word splitting, such as using
address@hidden"$str" $list} rather than @samp{"$str"$list}.
+
+There are also portability pitfalls with particular expansions:
+
 @table @code
 @item $@@
 @cindex @samp{"$@@"}
@@ -16202,6 +16228,20 @@ hence read-only.  Do not use it.
 Nowadays, it is difficult to find a shell that does not support
 shell functions at all.  However, some differences should be expected.
 
+When declaring a shell function, you must include whitespace between the
address@hidden)} after the function name and the start of the compound
+expression, to avoid upsetting @command{ksh}.  While it is possible to
+use any compound command, most scripts use @address@hidden@address@hidden
+
address@hidden
+$ @kbd{/bin/sh -c 'a()@{ echo hi;@}; a'}
+hi
+$ @kbd{ksh -c 'a()@{ echo hi;@}; a'}
+ksh: syntax error at line 1: address@hidden' unexpected
+$ @kbd{ksh -c 'a() @{ echo hi;@}; a'}
+hi
address@hidden example
+
 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
 @code{trap}, as this triggers bugs in zsh 4.x; while Autoconf tries to
@@ -16213,10 +16253,10 @@ function.  This has the effect that using a function 
as the first
 command in a @command{trap} handler can cause problems.
 
 @example
-$ @kbd{bash -c 'foo()@{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
+$ @kbd{bash -c 'foo() @{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
 2
 2
-$ @kbd{ash -c 'foo()@{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
+$ @kbd{ash -c 'foo() @{ echo $?; @}; trap foo 0; (exit 2); exit 2'; echo $?}
 0
 2
 @end example
@@ -16231,8 +16271,8 @@ Not all shells treat shell functions as simple commands 
impacted by
 @samp{set -e}, for example with Solaris 10 @command{bin/sh}:
 
 @example
-$ @kbd{bash -c 'f()@{ return 1; @}; set -e; f; echo oops}
-$ @kbd{/bin/sh -c 'f()@{ return 1; @}; set -e; f; echo oops}
+$ @kbd{bash -c 'f() @{ return 1; @}; set -e; f; echo oops}
+$ @kbd{/bin/sh -c 'f() @{ return 1; @}; set -e; f; echo oops}
 oops
 @end example
 
@@ -16259,13 +16299,13 @@ Meanwhile, not all shells follow the Posix rule that 
the assignment must
 affect the current environment in the same manner as special built-ins.
 
 @example
-$ @kbd{/bin/sh -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
+$ @kbd{/bin/sh -c 'func() @{ echo $a;@}; a=1 func; echo $a'}
 @result{}
 @result{}
-$ @kbd{ash -c 'func()@{ echo $a;@}; a=1 func; echo $a'}
+$ @kbd{ash -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 $a'}
+$ @kbd{bash -c 'set -o posix; func() @{ echo $a;@}; a=1 func; echo $a'}
 @result{}1
 @result{}1
 @end example


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