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, 9 insertions, 0 deletions

diff --git a/tests/misc/tac b/tests/misc/tac
index 2f9981d49..9995357ab 100755
--- a/tests/misc/tac
+++ b/tests/misc/tac
@@ -22,6 +22,8 @@ my $prog = 'tac';
 # Turn off localization of executable's output.
 @ENV{qw(LANGUAGE LANG LC_ALL)} = ('C') x 3;
 
+my $bad_dir = 'no/such/dir';
+
 my @Tests =
 (
   ['segfault', '-r', {IN=>"a\n"}, {IN=>"b\n"}, {OUT=>"a\nb\n"}],
@@ -58,6 +60,13 @@ my @Tests =
   ['opt-br2', qw(-b -r -s '\._+'),
    {IN=>".__x.___y.____z._1._2.__3.___4"},
    {OUT=>".___4.__3._2._1.____z.___y.__x"}],
+
+  ['pipe-bad-tmpdir',
+   {ENV => "TMPDIR=$bad_dir"},
+   {IN_PIPE => "a\n"},
+   {ERR_SUBST => "s,`$bad_dir': .*,...,"},
+   {ERR => "$prog: cannot create temporary file in ...\n"},
+   {EXIT => 1}],
 );
 
 @Tests = triple_test \@Tests;