[PATCH] nss_nisplus/nisplus-alias.c: fix build warning on gcc7

[Yury Norov <ynorov at caviumnetworks dot com>]

Hi all,

gcc7 for arm64 warns about NULL pointer passed to strlen() and
snprintf() in _nss_nisplus_getaliasbyname_r(). If Werror is enabled,
it is treaded as error, and so breask build:
nss_nisplus/nisplus-alias.c: In function
‘_nss_nisplus_getaliasbyname_r’:
nss_nisplus/nisplus-alias.c:300:12: error: argument 1 null where
non-null expected [-Werror=nonnull]
   char buf[strlen (name) + 9 + tablename_len];
            ^~~~~~~~~~~~~
In file included from ../include/string.h:54:0,
                 from nss_nisplus/nisplus-alias.c:23:
../string/string.h:394:15: note: in a call to function ‘strlen’ declared here
 extern size_t strlen (const char *__s)
               ^~~~~~
nss_nisplus/nisplus-alias.c:303:39: error: ‘%s’ directive argument is null [-Werror=format-truncation=]
   snprintf (buf, sizeof (buf), "[name=%s],%s", name, tablename_val);
				           ^~
cc1: all warnings being treated as errors

	* nis/nss_nisplus/nisplus-alias.c: don't pass name variable
	known to be NULL to strlen() and snprintf() in
	_nss_nisplus_getaliasbyname_r()

If the line "[name=],..." looks weird, I'll resend the patch, if someone will
hint me how it should look. Anyway, I think that it currently should look like
this.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
---
 nis/nss_nisplus/nisplus-alias.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nis/nss_nisplus/nisplus-alias.c b/nis/nss_nisplus/nisplus-alias.c
index 7f698b4e6d..509ace1f83 100644
--- a/nis/nss_nisplus/nisplus-alias.c
+++ b/nis/nss_nisplus/nisplus-alias.c
@@ -297,10 +297,10 @@ _nss_nisplus_getaliasbyname_r (const char *name, struct aliasent *alias,
       return NSS_STATUS_UNAVAIL;
     }
 
-  char buf[strlen (name) + 9 + tablename_len];
+  char buf[tablename_len + 9];
   int olderr = errno;
 
-  snprintf (buf, sizeof (buf), "[name=%s],%s", name, tablename_val);
+  snprintf (buf, sizeof (buf), "[name=],%s", tablename_val);
 
   nis_result *result = nis_list (buf, FOLLOW_PATH | FOLLOW_LINKS, NULL, NULL);
 
-- 
2.11.0