ext/snmp: improve GH-21341 test: wider walk subtree, trailing-dot check

Signed-off-by: Thomas Vincent <thomasvincent@gmail.com>

Author: somethingwithproof

ext/snmp/tests/gh21341.phpt

@@ -12,11 +12,12 @@ if (getenv('SKIP_ASAN')) die('skip Timeouts under ASAN');
 require_once(__DIR__.'/snmp_include.inc');
 
 /* Exercise the suffix-as-keys code path (SNMP_USE_SUFFIX_AS_KEYS |
- * SNMP_CMD_WALK).  The walk OID is chosen so the returned subidentifiers
- * form a multi-component suffix, driving multiple iterations of the
- * snprintf loop that GH-21341 replaced the strcat loop with. */
+ * SNMP_CMD_WALK).  Walking .1.3.6.1.2.1 (mib-2) returns entries whose
+ * suffixes have multiple components (e.g. "1.1.0", "2.1.1.0"), driving
+ * several iterations of the snprintf loop that GH-21341 replaced the
+ * strcat loop with. */
 $session = new SNMP(SNMP::VERSION_2c, $hostname, $community, $timeout, $retries);
-$result = $session->walk('.1.3.6.1.2.1.1', /* suffix_as_keys */ true);
+$result = $session->walk('.1.3.6.1.2.1', /* suffix_as_keys */ true);
 
 var_dump(is_array($result));
 var_dump(count($result) > 0);
@@ -28,10 +29,18 @@ $bad = array_filter(array_keys($result), static function (string $k): bool {
 });
 var_dump(count($bad) === 0);
 
+/* No key may end with '.': the trailing-dot removal (buf2[pos-1] = '\0')
+ * must fire correctly on every entry. */
+$trailing = array_filter(array_keys($result), static function (string $k): bool {
+    return $k !== '' && $k[-1] === '.';
+});
+var_dump(count($trailing) === 0);
+
 var_dump($session->close());
 ?>
 --EXPECT--
 bool(true)
 bool(true)
 bool(true)
 bool(true)
+bool(true)