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, 2 insertions, 1 deletions

diff --git a/src/tac.c b/src/tac.c
index 9cf6d60dc..c83986f59 100644
--- a/src/tac.c
+++ b/src/tac.c
@@ -454,7 +454,8 @@ copy_to_temp (FILE **g_tmp, char **g_tempfile, int input_fd, char const *file)
   fd = mkstemp (template);
   if (fd < 0)
     {
-      error (0, errno, _("cannot create temporary file %s"), quote (tempfile));
+      error (0, errno, _("cannot create temporary file in %s"),
+	     quote (tempdir));
       return false;
     }