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, 8 insertions, 4 deletions

diff --git a/src/mktemp.c b/src/mktemp.c
index 8a09231f9..d745e6069 100644
--- a/src/mktemp.c
+++ b/src/mktemp.c
@@ -242,20 +242,24 @@ main (int argc, char **argv)
                    quote (template));
         }
 
-      dest_name = file_name_concat (dest_dir, template, NULL);
+      template = file_name_concat (dest_dir, template, NULL);
     }
   else
     {
-      dest_name = xstrdup (template);
+      template = xstrdup (template);
     }
 
+  /* Make a copy to be used in case of diagnostic, since failing
+     mkstemp may leave the buffer in an undefined state.  */
+  dest_name = xstrdup (template);
+
   if (create_directory)
     {
       int err = mkdtemp_len (dest_name, x_count, dry_run);
       if (err != 0)
         {
           error (0, errno, _("failed to create directory via template %s"),
-                 quote (dest_name));
+                 quote (template));
           status = EXIT_FAILURE;
         }
     }
@@ -265,7 +269,7 @@ main (int argc, char **argv)
       if (fd < 0 || (!dry_run && close (fd) != 0))
         {
           error (0, errno, _("failed to create file via template %s"),
-                 quote (dest_name));
+                 quote (template));
           status = EXIT_FAILURE;
         }
     }