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Subject[PATCH v3] [SCSI] scsi_debug: silence GCC warning
From
Date
Building scsi_debug.o triggers a GCC warning:
drivers/scsi/scsi_debug.c: In function ‘dif_verify’:
drivers/scsi/scsi_debug.c:1755:3: warning: ‘csum’ may be used uninitialized in this function [-Wmaybe-uninitialized]

This warning was apparently introduced (in v3.11-rc1) by commit
beb40ea42b ("[SCSI] scsi_debug: reduce duplication between
prot_verify_read and prot_verify_write"). It is a false positive. But if
we transform the switch statement in dif_compute_csum() to a
straightforward if/else statement we supply GCC with enough information
to determine that csum will not be used uninitialized.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
---
0) v2: much simpler, and doesn't change any behavior;
v3: mention commit bebe40ea42b, as Akinobu suggested.

1) Still only compile tested.

drivers/scsi/scsi_debug.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index cb4fefa..7565ec5 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1735,14 +1735,11 @@ static u16 dif_compute_csum(const void *buf, int len)
{
u16 csum;

- switch (scsi_debug_guard) {
- case 1:
+ if (scsi_debug_guard == 1)
csum = ip_compute_csum(buf, len);
- break;
- case 0:
+ else
csum = cpu_to_be16(crc_t10dif(buf, len));
- break;
- }
+
return csum;
}

--
1.8.1.4
--
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