debug: Improve mqueue.h fortify warnings with clang

It improve mq_open.  The compile and runtime checks have similar
coverage as with GCC.

Checked on aarch64, armhf, x86_64, and i686.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

rt/bits/mqueue2.h

@@ -29,6 +29,8 @@ extern mqd_t __mq_open_2 (const char *__name, int __oflag)
 extern mqd_t __REDIRECT_NTH (__mq_open_alias, (const char *__name,
 					       int __oflag, ...), mq_open)
      __nonnull ((1));
+
+#ifdef __va_arg_pack_len
 __errordecl (__mq_open_wrong_number_of_args,
 	     "mq_open can be called either with 2 or 4 arguments");
 __errordecl (__mq_open_missing_mode_and_attr,
@@ -55,3 +57,30 @@ __NTH (mq_open (const char *__name, int __oflag, ...))
 
   return __mq_open_alias (__name, __oflag, __va_arg_pack ());
 }
+#elif __fortify_use_clang
+__fortify_function_error_function __attribute_overloadable__ mqd_t
+__NTH (mq_open (const char *__name, int __oflag, mode_t mode))
+     __fortify_clang_unavailable ("mq_open can be called either with 2 or 4 arguments");
+
+__fortify_function_error_function __attribute_overloadable__ mqd_t
+__NTH (mq_open (const char *__name, int __oflag, mode_t mode,
+		struct mq_attr *attr, ...))
+     __fortify_clang_unavailable ("mq_open can be called either with 2 or 4 arguments");
+
+__fortify_function __attribute_overloadable__ mqd_t
+__NTH (mq_open (__fortify_clang_overload_arg (const char *, ,__name),
+		int __oflag))
+     __fortify_clang_prefer_this_overload
+     __fortify_clang_error ((__oflag & O_CREAT),
+			     "mq_open with O_CREAT in second argument needs 4 arguments")
+{
+  return __mq_open_alias (__name, __oflag);
+}
+
+__fortify_function __attribute_overloadable__ mqd_t
+__NTH (mq_open (__fortify_clang_overload_arg (const char *, ,__name),
+		int __oflag, int __mode, struct mq_attr *__attr))
+{
+  return __mq_open_alias (__name, __oflag, __mode, __attr);
+}
+#endif

rt/mqueue.h

@@ -110,8 +110,7 @@ extern int __REDIRECT (mq_timedsend, (mqd_t __mqdes,
 #endif
 
 /* Define some inlines helping to catch common problems.  */
-#if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function \
-    && defined __va_arg_pack_len
+#if __USE_FORTIFY_LEVEL > 0 && defined __fortify_function
 # include <bits/mqueue2.h>
 #endif