Problems caused by ${1+"$@"}

[Rob Leslie]

Hello,

In several places, autoconf uses the shell idiom ${1+"$@"} to substitute 
the current positional parameters, if any. Unfortunately this is not 
completely portable; in particular, when Zsh is invoked as /bin/sh, word 
splitting is performed on the expanded parameters, so for example:

  'CPP=cc -E -traditional-cpp'

as one parameter becomes three:

  'CPP=cc' '-E' '-traditional-cpp'

This creates problems during argument parsing:

% ./configure CPP='cc -E -traditional-cpp'
configure: error: unrecognized option: -E
Try `./configure --help' for more information.

Even when such variables are passed through the environment, one may still 
later encounter problems:

% make
/bin/sh ./config.status --recheck
running /bin/sh ./configure  CPP=cc -E -traditional-cpp  --no-create 
--no-recursion
configure: error: unrecognized option: -E
Try `./configure --help' for more information.
make: *** [config.status] Error 1

I can suggest two possible solutions. One would be to use "$@" in place of 
${1+"$@"}, unless there was a special reason for the latter expression. (I 
don't have access to a lot of esoteric shells, but the Bourne-compatible 
ones I've tested, at least, remove the "$@" if there are no positional 
parameters.) Another possibility is to ensure Zsh is invoked as zsh rather 
than sh, or alternatively, execute 'unsetopt SH_WORD_SPLIT'. This may, 
however, break compatibility elsewhere if autoconf generally expects word 
splitting to be performed on unquoted $parameter expansions.

This is an important issue because under Mac OS X, /bin/sh is Zsh.

Thanks,

--
Rob Leslie
address@hidden