Unable to call private SerialBase functions

Mbed OS
6

I was not able to reproduce the reported runtime error when running the code below (built wit Mbed OS 6.4.0) on a NUCLEO_F446RE:

#include "mbed.h"

DigitalOut      led(LED1);
BufferedSerial  serial(USBTX, USBRX);
char            buf[64];
Thread          t;
EventQueue      eventQueue;

void onSerialReceived(void)
{
    char* p_buf = buf;

    memset(buf, 0, sizeof(buf));
    while (serial.readable()) {
        p_buf += serial.read(p_buf, sizeof(buf) - (p_buf - buf));
    }
    if (p_buf > buf) {
        printf("Received: %s\r\n", buf);
    }
}

void onSigio(void)
{
    eventQueue.call(onSerialReceived);
}

int main()
{
    printf("Starting...\r\n");
    t.start(callback(&eventQueue, &EventQueue::dispatch_forever));
    serial.sigio(callback(onSigio));
}

Maybe you have a mbed_app.json configuration file in your project affecting the build?