[PATCH blktests] blktests: Fix compilation warning

[Damien Le Moal <damien.lemoal@xxxxxxx>]

Fix strncpy length to "sizeof(buf) - 1" to avoid the compiler warning:
cc  -O2 -Wall -Wshadow  -o sg/syzkaller1 sg/syzkaller1.c
sg/syzkaller1.c: In function ‘syz_open_dev.constprop’:
sg/syzkaller1.c:204:16: warning: ‘strncpy’ specified bound 1024 equals
destination size [-Wstringop-truncation]
     NONFAILING(strncpy(buf, (char*)a0, sizeof(buf)));
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
sg/syzkaller1.c:143:7: note: in definition of macro ‘NONFAILING’
       __VA_ARGS__;                                                     \
       ^~~~~~~~~~~

Since the last character of buf is forced set to 0, there is no
functional change introduced by this patch.

Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
---
 src/sg/syzkaller1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/sg/syzkaller1.c b/src/sg/syzkaller1.c
index 60bd9a6..743859a 100644
--- a/src/sg/syzkaller1.c
+++ b/src/sg/syzkaller1.c
@@ -201,7 +201,7 @@ static uintptr_t syz_open_dev(uintptr_t a0, uintptr_t a1, uintptr_t a2)
   } else {
     char buf[1024];
     char* hash;
-    NONFAILING(strncpy(buf, (char*)a0, sizeof(buf)));
+    NONFAILING(strncpy(buf, (char*)a0, sizeof(buf) - 1));
     buf[sizeof(buf) - 1] = 0;
     while ((hash = strchr(buf, '#'))) {
       *hash = '0' + (char)(a1 % 10);
-- 
2.19.2