[PATCH 1/1 V2] Kselftest: msg_oob.c: Fix Compiler Warning For Incorrect Specifier

[David Hunter <david.hunter.linux@gmail.com>]

Change declaration to 'char *'. A specifier involved with a macro is
causing a misleading warning to occur:

'''
In file included from msg_oob.c:14:
msg_oob.c: In function ‘__recvpair’:
../../kselftest_harness.h:106:40: warning: format ‘%s’ expects
	argument of type ‘char *’, but argument 6 has type
	‘const void *’ [-Wformat=]
  106 |                 fprintf(TH_LOG_STREAM, "# %s:%d:%s:" fmt "\n", \
      |                                        ^~~~~~~~~~~~~
../../kselftest_harness.h:101:17: note: in expansion of macro ‘__TH_LOG’
  101 |                 __TH_LOG(fmt, ##__VA_ARGS__); \
      |                 ^~~~~~~~
msg_oob.c:235:17: note: in expansion of macro ‘TH_LOG’
  235 |                 TH_LOG("Expected:%s", expected_errno ?
			strerror(expected_errno) : expected_buf);
      |                 ^~~~~~
'''

I ran the tests using the following command:

'''
make kselftest TARGETS=net/af_unix
'''

I used a diff to examine the difference in output among the three
scenarios (1) before making the change, (2) after changing the
specifier, and (3) after changing the declaration. I saw no difference
in outputs among any of the tests; all three tests had the same exact
output.

For "net/af_unix: msg_oob", all 38 tests passed for msg_oob. I received
this result for all 3 scenarios. Should I have gotten a different
result?

Signed-off-by: David Hunter <david.hunter.linux@gmail.com>
---
Apologies for not looking ahead of time. I definitely need to remember
to check ahead of time. I understand that the other person was first; I
just wanted to get some practice sending patches. This is all still new
to me. 

V1 --> V2 
	- Changed the declaration instead of the specifier. 
	- Put number of patches for this bug fix. 
	- Put in tests performed. 

---
 tools/testing/selftests/net/af_unix/msg_oob.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/af_unix/msg_oob.c b/tools/testing/selftests/net/af_unix/msg_oob.c
index 16d0c172eaeb..535eb2c3d7d1 100644
--- a/tools/testing/selftests/net/af_unix/msg_oob.c
+++ b/tools/testing/selftests/net/af_unix/msg_oob.c
@@ -209,7 +209,7 @@ static void __sendpair(struct __test_metadata *_metadata,
 
 static void __recvpair(struct __test_metadata *_metadata,
 		       FIXTURE_DATA(msg_oob) *self,
-		       const void *expected_buf, int expected_len,
+		       const char *expected_buf, int expected_len,
 		       int buf_len, int flags)
 {
 	int i, ret[2], recv_errno[2], expected_errno = 0;
-- 
2.43.0