From: "Tim Van Holder" <tim DOT van DOT holder AT pandora DOT be>
To: <djgpp-workers AT delorie DOT com>
Subject: Re: New bash 2.04 beta release
Date: Tue, 10 Apr 2001 18:54:22 +0200
Message-ID: <CAEGKOHJKAAFPKOCLHDIEEFACCAA.tim.van.holder@pandora.be>
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> > Note that the ac_executable_extensions is a hack to avoid depending on
> > smart 'test -f' handling (EMX's bash doesn't have it).
> 
> Could you please tell more about this?  I don't think I understood
> what's that list for, exactly.

Before, the typical way of locating executables in autoconf was (in
pseudo-script):

: looking for foo
for dir in $PATH; do
  if test -f $dir/foo; then
    echo yay! foo is in $dir/foo
    break
  fi
done

I sent in a patch which ac_executable_exts variable that holds the
executable extensions for the host system. A search then does:

: looking for foo
for dir in $PATH; do
  if test -f $dir/foo; then
    echo yay! foo is in $dir/foo
    break
  elif test -n "$ac_executable_exts"; then
    for ext in $ac_executable_exts; do
      if test -f $dir/foo$ext; then
        echo yay! foo is in $dir/foo
        break
      fi
    done
  fi
done

This is definitely not optimal, but it worked just fine, even with
a bash that doesn't handle test -f specially.

This patch won't be in 2.50, though it will likely be in my DJGPP
package for 2.50.
autoconf 2.51 will have
 a) a way to build such a list itself, instead of relying on
    config.site to set it, and
 b) a cleaner way of dealing with it (avoiding the duplicated
    'if found' code).

One suggestion was to have a variable 'ac_executable_forms' instead,
which would default to '${base}'.

: looking for foo
for dir in $PATH; do
  forms=`base=foo eval echo $ac_executable_forms`
  for form in $forms; do
    if test -f $dir/$form; then
      echo yay! foo is in $dir/$form
      break
    fi
  done
done

That way, 'foo' would be found on Unixy systems; with the var set to
'i386-pc-msdosdjgpp-${base} ${base}' cross-compiling is made easy; and
with '${base} ${base}.exe ${base}.com ${base}.sh ${base}.pl ${base}.bat'
we get proper operation on DOS.

Hope this explains everything Eli :-)