Avoid outputting to TTY after an expected memory corruption in testcase

Protect TTY against an expected memory corruption from testcase
tst-malloc-backtrace, which is expected to SIGABRT after a forced memory
corruption.

ChangeLog

@@ -1,3 +1,8 @@
+2015-06-05  Tulio Magno Quites Machado Filho  <tuliom@linux.vnet.ibm.com>
+
+	* malloc/tst-malloc-backtrace.c (do_test): Redirect libc fatal
+	errors to stderr.
+
 2015-06-05  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #15661]

malloc/tst-malloc-backtrace.c

@@ -30,21 +30,26 @@ call_free (void *ptr)
   *(size_t *)(ptr - sizeof (size_t)) = 1;
 }
 
+int do_test (void);
+
+#define TEST_FUNCTION do_test ()
+#define EXPECTED_SIGNAL SIGABRT
+
+#include "../test-skeleton.c"
+
 int
 do_test (void)
 {
   void *ptr1 = malloc (SIZE);
   void *ptr2 = malloc (SIZE);
 
+  /* Avoid unwanted output to TTY after an expected memory corruption.  */
+  ignore_stderr();
+
   call_free (ptr1);
   ptr1 = malloc (SIZE);
 
   /* Not reached.  The return statement is to put ptr2 into use so that gcc
      doesn't optimize out that malloc call.  */
   return (ptr1 == ptr2);
 }
-
-#define TEST_FUNCTION do_test ()
-#define EXPECTED_SIGNAL SIGABRT
-
-#include "../test-skeleton.c"

test-skeleton.c

@@ -218,6 +218,22 @@ signal_handler (int sig __attribute__ ((unused)))
   exit (1);
 }
 
+/* Avoid all the buffer overflow messages on stderr.  */
+static void
+__attribute__ ((unused))
+ignore_stderr (void)
+{
+  int fd = open (_PATH_DEVNULL, O_WRONLY);
+  if (fd == -1)
+    close (STDERR_FILENO);
+  else
+    {
+      dup2 (fd, STDERR_FILENO);
+      close (fd);
+    }
+  setenv ("LIBC_FATAL_STDERR_", "1", 1);
+}
+
 /* Set fortification error handler.  Used when tests want to verify that bad
    code is caught by the library.  */
 static void
@@ -231,17 +247,7 @@ set_fortify_handler (void (*handler) (int sig))
   sigemptyset (&sa.sa_mask);
 
   sigaction (SIGABRT, &sa, NULL);
-
-  /* Avoid all the buffer overflow messages on stderr.  */
-  int fd = open (_PATH_DEVNULL, O_WRONLY);
-  if (fd == -1)
-    close (STDERR_FILENO);
-  else
-    {
-      dup2 (fd, STDERR_FILENO);
-      close (fd);
-    }
-  setenv ("LIBC_FATAL_STDERR_", "1", 1);
+  ignore_stderr ();
 }
 
 /* We provide the entry point here.  */