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

[Paul Eggert]

> 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

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.