On 04/07/2015 01:37 AM, Jan Engelhardt wrote:
On Tuesday 2015-04-07 02:38, Alexander Duyck wrote:
On 04/06/2015 11:05 AM, Arturo Borrero Gonzalez wrote:
linux_list.h:381:59: warning: right-hand operand of comma expression has no effect [-Wunused-value]
for (pos = list_entry((head)->next, typeof(*pos), member), \
^
libiptc.c:552:2: note: in expansion of macro 'list_for_each_entry'
list_for_each_entry(c, &h->chains, list) {
^
[ Patch copied from one similar of Patrick McHardy on libnftnl ]
Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@xxxxxxxxx>
---
libiptc/linux_list.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libiptc/linux_list.h b/libiptc/linux_list.h
index abdcf88..559e33c 100644
--- a/libiptc/linux_list.h
+++ b/libiptc/linux_list.h
@@ -27,7 +27,7 @@
1; \
})
-#define prefetch(x) 1
+#define prefetch(x) ((void)0)
/* empty define to make this work in userspace -HW */
#define smp_wmb()
Why not just use "do {} while (0)"? I know that is what is used in the
kernel for functions that don't do anything.
I may be getting the terms wrong, but:
do{}while(0) is not an expression, it is a (block) control statement.
In particular, do{}while(0) won't evaluate to an rvalue.
Right. That is the point in this case. I am assuming what Arturo is
trying to accomplish since you shouldn't be able to evaluate ((void)0)
as an rvalue either.
The prefetch(x) is an empty statement which is being cast as a void to
avoid a compiler warning, so it falls into the first case as defined in:
http://kernelnewbies.org/FAQ/DoWhile0
- Alex
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