Introduce a ZERO_OBJ macro similar to bzero

It uses `explicit_bzero` when available and falls back to `memset`
otherwise.

Conflicts:
	configure.ac

configure.ac

@@ -251,6 +251,7 @@ AC_CHECK_FUNCS([strerror])
 AC_FUNC_STRERROR_R
 AC_CHECK_FUNCS([dladdr])
 AC_CHECK_FUNCS([socket])
+AC_CHECK_FUNCS([explicit_bzero])
 AC_CHECK_FUNCS([nanosleep])
 AC_CHECK_FUNCS([setppriv])
 AC_CHECK_FUNCS([fallocate])

include/miniobj.h

@@ -5,6 +5,12 @@
  *
  */
 
+#if HAVE_EXPLICIT_BZERO
+#  define ZERO_OBJ(to, sz)	explicit_bzero(to, sz)
+#else
+#  define ZERO_OBJ(to, sz)	(void)memset(to, 0, sz)
+#endif
+
 #define INIT_OBJ(to, type_magic)					\
 	do {								\
 		(void)memset(to, 0, sizeof *to);			\
@@ -20,7 +26,7 @@
 
 #define FREE_OBJ(to)							\
 	do {								\
-		(to)->magic = (0);					\
+		ZERO_OBJ(&(to)->magic, sizeof (to)->magic);		\
 		free(to);						\
 		to = NULL;						\
 	} while (0)