On 05/15/15 05:33, Tijl Coosemans wrote:
Modified: head/sys/sys/cdefs.h
==============================================================================
--- head/sys/sys/cdefs.h Thu May 14 15:14:03 2015 (r282906)
+++ head/sys/sys/cdefs.h Thu May 14 15:49:48 2015 (r282907)
@@ -388,6 +388,12 @@
#define __alloc_size(x)
#endif
+#if __has_builtin(__builtin_unreachable) || __GNUC_PREREQ__(4, 6)
+#define __unreachable() __builtin_unreachable()
+#else
+#define __unreachable() do {} while (/*CONSTCOND*/0)
__builtin_unreachable() can be used in expressions so I think it's better
to replace do-while with ((void)0). You can then do things like this:
#define assume(e) ((e) ? (void)0 : __unreachable())
(like assert(e) but without error)
Looks reasonable, thanks!
FWIW, there was some discussion about having a debugging
macro that warns when such unreachable code is reached.
We are just not sure where such a macro belongs, probably
not in cdefs.
Pedro.
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