Do not copy MYSQL_TS if length is 0

Related to issue #3585

A prepared statement with buffer_type = MYSQL_TYPE_TIME (or similar like
MYSQL_TYPE_DATE, etc) can have length = 0 if the time is 0. In this case
no data needs to be copied from COM_STMT_EXECUTE packet

lib/MySQL_Protocol.cpp

@@ -2231,11 +2231,14 @@ stmt_execute_metadata_t * MySQL_Protocol::get_binds_from_pkt(void *ptr, unsigned
 			uint8_t null_byte=null_bitmap[i/8];
 			uint8_t idx=i%8;
 			my_bool is_null = (null_byte & ( 1 << idx )) >> idx;
+			if (binds[i].buffer_type == MYSQL_TYPE_NULL)
+				is_null = 1;
 			is_nulls[i]=is_null;
 			binds[i].is_null=&is_nulls[i];
 			// set length, defaults to 0
 			// for parameters with not fixed length, that will be assigned later
 			// we moved this initialization here due to #3585
+			binds[i].is_unsigned=0;
 			lengths[i]=0;
 			binds[i].length=&lengths[i];
 			// NOTE: We nullify buffers here to reflect that memory wasn't
@@ -2307,11 +2310,13 @@ stmt_execute_metadata_t * MySQL_Protocol::get_binds_from_pkt(void *ptr, unsigned
 						p++;
 						MYSQL_TIME ts;
 						memset(&ts,0,sizeof(MYSQL_TIME));
-						memcpy(&ts.neg,p,1);
-						memcpy(&ts.day,p+1,4);
-						memcpy(&ts.hour,p+5,1);
-						memcpy(&ts.minute,p+6,1);
-						memcpy(&ts.second,p+7,1);
+						if (l) {
+							memcpy(&ts.neg,p,1);
+							memcpy(&ts.day,p+1,4);
+							memcpy(&ts.hour,p+5,1);
+							memcpy(&ts.minute,p+6,1);
+							memcpy(&ts.second,p+7,1);
+						}
 						if (l>8) {
 							memcpy(&ts.second_part,p+8,4);
 						}
@@ -2329,9 +2334,11 @@ stmt_execute_metadata_t * MySQL_Protocol::get_binds_from_pkt(void *ptr, unsigned
 						p++;
 						MYSQL_TIME ts;
 						memset(&ts,0,sizeof(MYSQL_TIME));
-						memcpy(&ts.year,p,2);
-						memcpy(&ts.month,p+2,1);
-						memcpy(&ts.day,p+3,1);
+						if (l) {
+							memcpy(&ts.year,p,2);
+							memcpy(&ts.month,p+2,1);
+							memcpy(&ts.day,p+3,1);
+						}
 						if (l>4) {
 							memcpy(&ts.hour,p+4,1);
 							memcpy(&ts.minute,p+5,1);

test/tap/tests/reg_test_3585-stmt_metadata-t.cpp

@@ -315,7 +315,7 @@ int main(int argc, char** argv) {
 	}
 
 	int np = 4; // init + prepare
-	np += 21*2; // number of INSERT+SELECT
+	np += 25*2; // number of INSERT+SELECT
 	plan(np);
 
 	MYSQL* proxysql_mysql = mysql_init(NULL);
@@ -414,6 +414,12 @@ int main(int argc, char** argv) {
 	insert_and_check(stmti, stmts, 19, NULL,              NULL, NULL, NULL,             NULL, &i2);
 	insert_and_check(stmti, stmts, 20, NULL,              NULL, &i1,  NULL,             NULL, &i2);
 	insert_and_check(stmti, stmts, 21, NULL,              &ts1, &i1,  NULL,             NULL, &i2);
+	ts1.hour = 0; ts1.minute = 0; ts1.second=0;
+	ts2.hour = 0; ts2.minute = 0; ts2.second=0;
+	insert_and_check(stmti, stmts, 22, NULL,              &ts1, NULL, (char *)"world22", &ts2, NULL);
+	insert_and_check(stmti, stmts, 23, (char *)"hello23", NULL, NULL, (char *)"world23", &ts2, NULL);
+	insert_and_check(stmti, stmts, 24, (char *)"hello24", NULL, &i1,  NULL,              NULL, &i2);
+	insert_and_check(stmti, stmts, 25, NULL,              NULL, NULL, (char *)"world25", &ts2, &i2);
 	mysql_close(proxysql_mysql);
 	mysql_close(proxysql_admin);