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, 3 insertions, 2 deletions

diff --git a/tests/misc/sort-merge b/tests/misc/sort-merge
index 985d7a414..6b8192610 100755
--- a/tests/misc/sort-merge
+++ b/tests/misc/sort-merge
@@ -66,8 +66,9 @@ my @Tests =
      # this should fail since nmerge < # of input files, so
      # temp files are needed
      ['nmerge-no', "-m --batch-size=2 -T$badtmp", @inputs,
-        {ERR_SUBST=>"s|: $badtmp/sort.+||"},
-        {ERR=>"$prog: cannot create temporary file\n"}, {EXIT=>2}],
+        {ERR_SUBST=>"s|': .*|':|"},
+        {ERR=>"$prog: cannot create temporary file in `$badtmp':\n"},
+	{EXIT=>2}],
 
      # This used to fail because setting batch-size without also setting
      # buffer size would cause the buffer size to be set to the minimum.