random characters after the 64th on c++ mysql - c++

Question

I'm facing a very strange issue while interacting with mysql db through my c++ app.
environment:
docker-compose.yml
version: '3.1'
services:
db:
image: mysql:8.0.21 #libmysqlcppconn8-2_8.0.21-1ubuntu18.04_amd64.deb connector
command: --default-authentication-plugin=mysql_native_password
restart: always
environment:
MYSQL_ROOT_PASSWORD: example
security_opt:
- seccomp:unconfined
client:
build: .
ports:
- "2890:2890"
Client container is ubuntu18.04, here a simple code to test connection and a minimum result:
#include <cstdio>
#include <iostream>
#include <stdlib.h>
#include <unistd.h>
#include "mysql_connection.h"
#include <array>
#include <cppconn/driver.h>
#include <cppconn/exception.h>
#include <cppconn/prepared_statement.h>
#include <cppconn/resultset.h>
#include <cppconn/statement.h>
int main() {
sql::Driver *driver = get_driver_instance();
sql::Connection *con =
driver->connect("tcp://remote_backup_db_1", "root", "example");
con->setSchema("db_test");
sql::PreparedStatement *stmt;
sql::ResultSet *res;
stmt = con->prepareStatement("SELECT test from t;");
res = stmt->executeQuery();
if (res->rowsCount() > 0) {
if (res->next()) {
std::string text = res->getString("test");
std::clog << "text: " << text << "\n";
}
}
return 0;
}
here is a describe of the table:
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| test | varchar(128) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
issue: when I try to retrieve a text that is less than 64 bytes everything works properly, but when I try to execute the same code with a text greater than 64 bytes it retrieves the firts 64 bytes followed by random characters. The problem seems not to be related to the column type (same problem with blob for example). It seems to be related with encoding because when i try to get the result length, it is set properly (e.g with a 70 character text long it gives me 70).
I've already tried to change table encoding and I don't know how to solve this. (ps I'm not using strange characters only ASCII basically).