Re: Libtool and echo (Was: bison-1.29c 'configure' problems on Solaris 8)

[Gary V. Vaughan]

On Fri, Oct 05, 2001 at 06:22:43PM -0700, Paul Eggert wrote:
> > From: "Gary V. Vaughan" <address@hidden>
> > Date: Fri, 5 Oct 2001 22:46:36 +0100
> > 
> > libtool needs to store lots of script snippets in shell variables to
> > be passed to eval later.  In order for this to work, it must be
> > possible to backslash escape shell meta characters, so that eval's
> > behaviour is predictable.
> 
> In this case I don't think it's feasible to require a POSIX shell on
> the part of the installer, as you probably still want to run on bare
> SunOS 4.1.4.  So it's a somewhat different case from LINENO, which
> isn't needed for correct operation of "configure".
> 
> That being said, have you tried doing something like this as a replacement
> for escaped_something=`echo "$something" | sed 's/\\/\\\\/g'`?
> 
>   case $something in
>   *\\*)
>     awk_script='{
>       input=$0
>       output=""
>       while ((i = index(input, "\\")) != 0) {
>       output = output substr(input, 1, i) "\\"
>       input = substr(input, i + 1)
>       }
>       print output input
>     }'
>     escaped_something=`awk "$awk_script" <<EOF
> $something
> EOF
>     `
>     ;;
>   *)
>     escaped_something=$something;;
>   esac

No, I haven't tried this sort of thing.  But I am willing to
experiment on the HEAD branch.  Unfortunately, my hacking time is much
reduced for the next month or three so I am barely managing to keep up
with patch submissions.

> This is a bit hard to read, but it is quite portable and you can
> package it up into an Autoconf macro.  And in the common case where
> $something contains no backslashes, this solution runs about 50 times
> faster than the echo|sed solution (at least, on my Solaris 8 box).
> 
> Maybe something like this should be added to Autoconf.  Certainly
> Autoconf is now buggy in more than one place, if "configure" is passed
> operands that contain backslashes.

I think this is certainly worth a try.  If it works out, we would then
be in a position to think about reexecing with a shell that supports
functions (cf. my other mail in this thread), and configure scripts
could be a whole lot shorter!

Cheers,
        Gary.

-- 
  ())_. Gary V. Vaughan     gary@(oranda.demon.co.uk|gnu.org)
  ( '/  Research Scientist  http://www.oranda.demon.co.uk       ,_())____
  / )=  GNU Hacker          http://www.gnu.org/software/libtool  \'      `&
`(_~)_  Tech' Author        http://sources.redhat.com/autobook   =`---d__/