Replace tmpnam() based filename generation with race free version

The tempfile() interface in File::Temp is race free and has been
available as a core module since Perl 5.6.1 (released in April
2001) so replace to simplify the code and avoid excessive looping
around a solved problem.

src/test/regress/atmsort.pm

@@ -20,6 +20,7 @@ package atmsort;
 use strict;
 use warnings;
 use File::Spec;
+use File::Temp qw/ tempfile /;
 
 # Load explain.pm from the same directory where atmsort.pm is.
 use FindBin;
@@ -1627,19 +1628,21 @@ L_push_outarr:
 } # end bigloop
 
 
-# The arguments are input and output file names
+# The arguments is the input filename. The output filename is returned as it
+# is generated in this function to avoid races around the temporary filename
+# creation.
 sub run
 {
     my $infname = shift;
-    my $outfname = shift;
 
     open my $infh,  '<', $infname  or die "could not open $infname: $!";
-    open my $outfh, '>', $outfname or die "could not open $outfname: $!";
+    my ($outfh, $outfname) = tempfile();
 
     run_fhs($infh, $outfh);
 
     close $infh;
     close $outfh;
+    return $outfname;
 }
 
 # The arguments are input and output file handles

src/test/regress/gpdiff.pl

@@ -150,6 +150,8 @@ sub gpdiff_files
     my ($f1, $f2, $d2d) = @_;
     my $need_equiv = 0;
     my @tmpfils;
+    my $newf1;
+    my $newf2;
 
     # need gnu diff on solaris
     if ($Config{'osname'} =~ m/solaris|sunos/i)
@@ -157,40 +159,22 @@ sub gpdiff_files
         $ATMDIFF = "gdiff";
     }
 
-    for my $ii (1..2)
-    {
-        my $tmpnam;
-
-        for (;;)
-        {
-            my $tmpfh;
-
-            $tmpnam = tmpnam();
-            sysopen($tmpfh, $tmpnam, O_RDWR | O_CREAT | O_EXCL) && last;
-        }
-
-        push @tmpfils, $tmpnam;
-    }
-
-    my $newf1 = shift @tmpfils;
-    my $newf2 = shift @tmpfils;
-
 #    print $glob_atmsort_args, "\n";
 
     if (defined($d2d) && exists($d2d->{equiv}))
     {
         # assume f1 and f2 are the same...
         atmsort::atmsort_init(%glob_atmsort_args, DO_EQUIV => 'compare');
-        atmsort::run($f1, $newf1);
+        $newf1 = atmsort::run($f1);
 
         atmsort::atmsort_init(%glob_atmsort_args, DO_EQUIV => 'make');
-        atmsort::run($f2, $newf2);
+        $newf2 = atmsort::run($f2);
     }
     else
     {
         atmsort::atmsort_init(%glob_atmsort_args);
-        atmsort::run($f1, $newf1);
-        atmsort::run($f2, $newf2);
+        $newf1 = atmsort::run($f1);
+        $newf2 = atmsort::run($f2);
     }
 
     my $args = join(" ", @ARGV, $newf1, $newf2);