Re: [PATCH] mm: cleanup swap unused warning

On Wednesday 10 May 2006 21:38, Andrew Morton wrote:
Con Kolivas <kernel@xxxxxxxxxxx> wrote:
Are there any users of swp_entry_t when CONFIG_SWAP is not defined?

Well there shouldn't be. Making accesses to swp_entry_t.val fail to
compile if !CONFIG_SWAP might be useful.

+/*
+ * A swap entry has to fit into a "unsigned long", as
+ * the entry is hidden in the "index" field of the
+ * swapper address space.
+ */
+#ifdef CONFIG_SWAP
typedef struct {
unsigned long val;
} swp_entry_t;
+#else
+typedef struct {
+ unsigned long val;
+} swp_entry_t __attribute__((__unused__));
+#endif

We have __attribute_used__, which hides a gcc oddity.

I tried that.

In file included from arch/i386/mm/pgtable.c:11:
include/linux/swap.h:82: warning: ‘__used__’ attribute ignored
In file included from include/linux/suspend.h:8,
from init/do_mounts.c:7:
include/linux/swap.h:82: warning: ‘__used__’ attribute ignored
In file included from arch/i386/mm/init.c:22:
include/linux/swap.h:82: warning: ‘__used__’ attribute ignored
AS arch/i386/kernel/vsyscall-sysenter.o

etc..

and doesn't fix the warning in vmscan.c. __attribute_used__ is handled
differently by gcc4 it seems (this is 4.1.0)

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