Rewrite. abs_path() fails if path components before the last don't exist.

configure/tools/fullPathName.pl

@@ -1,20 +1,40 @@
 eval 'exec perl -S -w  $0 ${1+"$@"}'  # -*- Mode: perl -*-
-        if 0; 
+    if 0;
 
-#
-# Determine fullpathname if argument starts with "."
-# else return argument value.
-#
+# Determines an absolute pathname for its argument,
+# which may be either a relative or absolute path and
+# might have trailing parts that don't exist yet.
 
-use Cwd 'abs_path';
-my $dir;
-if( $ARGV[0] ) {
-  if( $ARGV[0] =~ /^\./ )
-  {
-    $dir = abs_path("$ARGV[0]");
-	$dir =~ s/\/tmp_mnt//;     
-    print "$dir\n";
-  } else  {
-    print "$ARGV[0]\n";
-  }
+use strict;
+use Cwd qw(getcwd abs_path);
+use File::Spec;
+
+# Starting values
+my $cwd = getcwd();
+my $rel = shift;
+
+$rel = '.' unless defined $rel;
+
+# Move leading ./ and ../ components from $rel to $cwd
+if (my ($dot, $not) = ($rel =~ m[^ ( (?: \. \.? / )+ ) ( .* ) $]x)) {
+    $cwd .= "/$dot";
+    $rel = $not;
 }
+
+# Handle a pure ..
+if ($rel eq '..') {
+    $cwd .= '/..';
+    $rel = '.'
+}
+
+# NB: abs_path() doesn't like non-existent path components other than
+# in the final position, which is why we use this method.
+
+# Calculate the absolute path
+my $abs = File::Spec->rel2abs($rel, abs_path($cwd));
+
+# Remove any automounter prefixes
+$abs =~ s[^ /tmp_mnt ][]x;              # SunOS, HPUX
+$abs =~ s[^ /private/var/auto\. ][/]x;  # MacOS
+
+print "$abs\n";