+sub exim_binary {
+
+ # two simple cases, absolute path or relative path and executable
+ return @_ if $_[0] =~ /^\//;
+ return Cwd::abs_path(shift), @_ if -x $_[0];
+
+ # so we're still here, if the simple approach didn't help.
+
+ # if there is '../exim-snapshot/<build-dir>/exim', use this
+ # if there is '../exim4/<build-dir>/exim', use this
+ # if there is '../exim-*.*/<build-dir>/exim', use the one with the highest version
+ # 4.84 < 4.85RC1 < 4.85RC2 < 4.85 < 4.86RC1 < … < 4.86
+ # if there is '../src/<build-dir>', use this
+ #
+
+ my $prefix = '..'; # was intended for testing.
+
+ # get a list of directories having the "scripts/{os,arch}-type"
+ # scripts
+ my @candidates = grep { -x "$_/scripts/os-type" and -x "$_/scripts/arch-type" }
+ "$prefix/exim-snapshot", "$prefix/exim4", # highest priority
+ (reverse sort { # list of exim-*.* directories
+ # split version number from RC number
+ my @a = ($a =~ /(\d+\.\d+)(?:RC(\d+))?/);
+ my @b = ($b =~ /(\d+\.\d+)(?:RC(\d+))?/);
+ # if the versions are not equal, we're fine,
+ # but otherwise we've to compare the RC number, where an
+ # empty RC number is better than a non-empty
+ ($a[0] cmp $b[0]) || (defined $a[1] ? defined $b[1] ? $a[1] cmp $b[1] : -1 : 1)
+ } glob "$prefix/exim-*.*"),
+ "$prefix/src"; # the "normal" source
+
+ # binaries should be found now depending on the os-type and
+ # arch-type in the directories we got above
+ my @binaries = grep { -x }
+ map { ("$_/exim", "$_/exim4") }
+ map {
+ my $os = `$_/scripts/os-type`;
+ my $arch = `$_/scripts/arch-type`;
+ chomp($os, $arch);
+ "$_/build-$os-$arch" . ($ENV{EXIM_BUILD_SUFFIX} ? ".$ENV{EXIM_BUILD_SUFFIX}" : '');
+ } @candidates;
+
+ return $binaries[0], @_;
+}
+
+