ReadFile() says it failed, but the error code is ERROR_SUCCESS

Question

I\'m using ReadFile() on Windows to read data from a serial port. This code was working fine at one point in time, but it\'s now failing and I\'m trying to trac

Answer 1

The constructor of QMessageBox may be doing something that clears `GetLastError'. Try this:

if (!ReadFile(hGpsUart, buf, 160, &bytes_read, NULL)) 
{
    int LastError = GetLastError() ;
    QMessageBox msg;
    msg.setText(QString("Error %1 reading from GPS UART!").arg(LastError));
    msg.exec();
}