mktemp, sort, tac: don't use undefined after mkstemp failure

When mkstemp fails, the template buffer may have undefined
contents, so we must not print it.
* src/sort.c (create_temp_file): Use temp_dir, not "file"
when diagnosing failed mkstemp, because "file" may be undefined.
* tests/misc/sort-merge: Adjust for new expected output.
Jeph Cowan and Ralf Wildenhues reported the test failure:
http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/14235/focus=14257
* src/tac.c (copy_to_temp): Don't use template buffer after
failed mkstemp call, since its contents may be undefined.
* tests/misc/tac (pipe-bad-tmpdir): New test for the above.
* src/mktemp.c (main): Save a copy of the template string,
solely for use in case mkstemp fails.
* tests/misc/mktemp (pipe-bad-tmpdir): New test for the above.

1 files changed, 7 insertions, 0 deletions

diff --git a/tests/misc/mktemp b/tests/misc/mktemp
index 616a9e44f..356558291 100755
--- a/tests/misc/mktemp
+++ b/tests/misc/mktemp
@@ -49,6 +49,7 @@ sub check_tmp($$)
 # Turn off localization of executable's output.
 @ENV{qw(LANGUAGE LANG LC_ALL)} = ('C') x 3;
 my $prog = 'mktemp';
+my $bad_dir = 'no/such/dir';
 
 my @Tests =
     (
@@ -97,6 +98,12 @@ my @Tests =
       {POST => sub { my ($f) = @_; defined $f or return; chomp $f;
        check_tmp $f, 'F'; unlink $f; rmdir 'a' or die "rmdir a: $!\n" }}
      ],
+
+     ['pipe-bad-tmpdir',
+      {ENV => "TMPDIR=$bad_dir"},
+      {ERR_SUBST => "s,($bad_dir/)[^']+': .*,\$1...,"},
+      {ERR => "$prog: failed to create file via template `$bad_dir/...\n"},
+      {EXIT => 1}],
     );
 
 my $save_temps = $ENV{DEBUG};