Fix for Issue #16910

Prevent truncation of fractional seconds in binary protocol if server
sends AUTO_SEC_PART_DIGITS (value=39) in decimals value of metadata
for TIME or DATETIME types.

Author: 9EOR9

ext/mysqli/tests/gh16910.phpt

@@ -0,0 +1,40 @@
+--TEST--
+GH-xxxxx (AUTO_SEC_PART_DIGITS (field->decimal value=39) ignored in binary protocol)
+--EXTENSIONS--
+mysqli
+--SKIPIF--
+<?php
+require_once 'skipifconnectfailure.inc';
+?>
+--FILE--
+<?php
+require_once 'connect.inc';
+
+if (!$link = my_mysqli_connect($host, $user, $passwd, $db, $port, $socket)) {
+    printf("Cannot connect to the server using host=%s, user=%s, passwd=***, dbname=%s, port=%s, socket=%s\n",
+        $host, $user, $db, $port, $socket);
+    exit(1);
+}
+
+// Values from binary and text protocol should be the same
+$stmt = $link->prepare("select FROM_UNIXTIME('1992.1'), FROM_UNIXTIME('1992.0')");
+$stmt->execute();
+$stmt->bind_result($binval[0],$binval[1]);
+$stmt->fetch();
+$stmt->close();
+
+$result = $link->query("select FROM_UNIXTIME('1992.1'), FROM_UNIXTIME('1992.0')");
+$txtval = $result->fetch_row();
+$result->close();
+$err_cnt= 0;
+
+for ($i=0; $i < 2; $i++)
+    if ($txtval[$i] != $binval[$i])
+        printf("[%03d] Expected '%s' (text protocol), got '%s' (binary protocol)",
+               $err_cnt++, $txtval[$i], $binval[$i]);
+
+if ($err_cnt == 0)
+    print "done!";
+?>
+--EXPECT--
+done!

ext/mysqlnd/mysqlnd_ps_codec.c

@@ -50,6 +50,9 @@ struct st_mysqlnd_perm_bind mysqlnd_ps_fetch_functions[MYSQL_TYPE_LAST + 1];
 #define MYSQLND_PS_SKIP_RESULT_W_LEN	-1
 #define MYSQLND_PS_SKIP_RESULT_STR		-2
 
+#define MYSQLND_SEC_PART_DIGITS        6
+#define MYSQLND_AUTO_SEC_PART_DIGITS  39
+
 /* {{{ ps_fetch_from_1_to_8_bytes */
 void
 ps_fetch_from_1_to_8_bytes(zval * zv, const MYSQLND_FIELD * const field, const unsigned int pack_len,
@@ -237,7 +240,9 @@ ps_fetch_time(zval * zv, const MYSQLND_FIELD * const field, const unsigned int p
 		t.time_type = MYSQLND_TIMESTAMP_TIME;
 	}
 
-	if (field->decimals > 0 && field->decimals < 7) {
+	if (field->decimals > 0 && (field->decimals <= MYSQLND_SEC_PART_DIGITS ||
+                             (field->decimals == MYSQLND_AUTO_SEC_PART_DIGITS && t.second_part))) {
+    uint8_t decimals= (field->decimals == MYSQLND_AUTO_SEC_PART_DIGITS) ? MYSQLND_SEC_PART_DIGITS : field->decimals;
 		ZVAL_STR(zv, zend_strpprintf(0, "%s%02u:%02u:%02u.%0*u",
 			(t.neg ? "-" : ""), t.hour, t.minute, t.second, field->decimals,
 			(uint32_t) (t.second_part / pow(10, 6 - field->decimals))));
@@ -315,10 +320,12 @@ ps_fetch_datetime(zval * zv, const MYSQLND_FIELD * const field, const unsigned i
 		t.time_type = MYSQLND_TIMESTAMP_DATETIME;
 	}
 
-	if (field->decimals > 0 && field->decimals < 7) {
+	if (field->decimals > 0 && (field->decimals <= MYSQLND_SEC_PART_DIGITS ||
+                             (field->decimals == MYSQLND_AUTO_SEC_PART_DIGITS && t.second_part))) {
+    uint8_t decimals= (field->decimals == MYSQLND_AUTO_SEC_PART_DIGITS) ? MYSQLND_SEC_PART_DIGITS : field->decimals;
 		ZVAL_STR(zv, zend_strpprintf(0, "%04u-%02u-%02u %02u:%02u:%02u.%0*u",
-			t.year, t.month, t.day, t.hour, t.minute, t.second, field->decimals,
-			(uint32_t) (t.second_part / pow(10, 6 - field->decimals))));
+			t.year, t.month, t.day, t.hour, t.minute, t.second, decimals,
+			(uint32_t) (t.second_part / pow(10, 6 - decimals))));
 	} else {
 		ZVAL_STR(zv,  zend_strpprintf(0, "%04u-%02u-%02u %02u:%02u:%02u",
 			t.year, t.month, t.day, t.hour, t.minute, t.second));