[PATCH] MIPS: prevent compiler warning from cop2_{save,restore}

[Paul Burton]

The no-op cases of cop2_save & cop2_restore lead to the following
warnings being emitted during build with recent versions of gcc (tested
using gcc 4.8.3 from the Mentor Sourcery CodeBench 2014.05 toolchain):

In file included from ./arch/mips/include/asm/switch_to.h:18:0,
from kernel/sched/core.c:78:
kernel/sched/core.c: In function 'finish_task_switch':
include/asm-generic/current.h:6:45: warning: value computed is not used [-Wunused-value]
#define get_current() (current_thread_info()->task)
^
./arch/mips/include/asm/cop2.h:48:32: note: in definition of macro 'cop2_restore'
#define cop2_restore(r) do { (r); } while (0)
^
include/asm-generic/current.h:7:17: note: in expansion of macro 'get_current'
#define current get_current()
^
./arch/mips/include/asm/switch_to.h:114:16: note: in expansion of macro 'current'
cop2_restore(current); \
^
kernel/sched/core.c:2225:2: note: in expansion of macro 'finish_arch_switch'
finish_arch_switch(prev);
^

Avoid the warning by "using" the value by casting to void.

Signed-off-by: Paul Burton <***@imgtec.com>
---
arch/mips/include/asm/cop2.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/mips/include/asm/cop2.h b/arch/mips/include/asm/cop2.h
index 51f80bd..63b3468 100644
--- a/arch/mips/include/asm/cop2.h
+++ b/arch/mips/include/asm/cop2.h
@@ -37,15 +37,15 @@ extern void nlm_cop2_restore(struct nlm_cop2_state *);

#define cop2_present 1
#define cop2_lazy_restore 1
-#define cop2_save(r) do { (r); } while (0)
-#define cop2_restore(r) do { (r); } while (0)
+#define cop2_save(r) do { (void)(r); } while (0)
+#define cop2_restore(r) do { (void)(r); } while (0)

#else

#define cop2_present 0
#define cop2_lazy_restore 0
-#define cop2_save(r) do { (r); } while (0)
-#define cop2_restore(r) do { (r); } while (0)
+#define cop2_save(r) do { (void)(r); } while (0)
+#define cop2_restore(r) do { (void)(r); } while (0)
#endif

enum cu2_ops {

[Sergei Shtylyov]

Hello.

Post by Paul Burton
The no-op cases of cop2_save & cop2_restore lead to the following
warnings being emitted during build with recent versions of gcc (tested
In file included from ./arch/mips/include/asm/switch_to.h:18:0,
include/asm-generic/current.h:6:45: warning: value computed is not used [-Wunused-value]
#define get_current() (current_thread_info()->task)

^

Post by Paul Burton
./arch/mips/include/asm/cop2.h:48:32: note: in definition of macro 'cop2_restore'
#define cop2_restore(r) do { (r); } while (0)
^
include/asm-generic/current.h:7:17: note: in expansion of macro 'get_current'
#define current get_current()
^
./arch/mips/include/asm/switch_to.h:114:16: note: in expansion of macro 'current'
cop2_restore(current); \
^
kernel/sched/core.c:2225:2: note: in expansion of macro 'finish_arch_switch'
finish_arch_switch(prev);
^
Avoid the warning by "using" the value by casting to void.
---
arch/mips/include/asm/cop2.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/mips/include/asm/cop2.h b/arch/mips/include/asm/cop2.h
index 51f80bd..63b3468 100644
--- a/arch/mips/include/asm/cop2.h
+++ b/arch/mips/include/asm/cop2.h
@@ -37,15 +37,15 @@ extern void nlm_cop2_restore(struct nlm_cop2_state *);
#define cop2_present 1
#define cop2_lazy_restore 1
-#define cop2_save(r) do { (r); } while (0)
-#define cop2_restore(r) do { (r); } while (0)
+#define cop2_save(r) do { (void)(r); } while (0)
+#define cop2_restore(r) do { (void)(r); } while (0)
#else
#define cop2_present 0
#define cop2_lazy_restore 0
-#define cop2_save(r) do { (r); } while (0)
-#define cop2_restore(r) do { (r); } while (0)
+#define cop2_save(r) do { (void)(r); } while (0)
+#define cop2_restore(r) do { (void)(r); } while (0)
#endif

Looks like the definition are identical between 2 arms of #if, so why not
move the macro definition out of #if, perhaps in later cleanup patch?

WBR, Sergei