Reading String on Serial COM Port

There are multiple mistakes: use of C-strings instead of std::string, no bound checks, e.t.c.:

BOOL ReadString(char *outstring)
{
    int *length; // !!!! length is not initialized, it may point to any address
    *length = sizeof(int);

    BYTE data;
    BYTE dataout[8192]={0};
    int index = 0;

    while(ReadByte(data)== TRUE) // !!!! No bound check. What if index will become more than 8192?
    {
        dataout[index++] = data;
    }
    memcpy(outstring, dataout, index);
    *length = index; // Hmm, length is not static it is automatic variable and will not keep the index between the calls

    return TRUE;
}

In main:

int main(void)
{
    //  Configs
    hPort = ConfigureSerialPort("COM1");
    if(hPort == NULL)
    {
        printf("Com port configuration failed\n");
        return -1;
    }


    char* cPTR; // !!!! Not initialized, points to any place in memory
    for(;;)
    {
      ReadString(cPTR); // !!!! cPTR not allocated, you pass the pointer to somwhere

      if(cPTR!=NULL)
        cout << "Scanned Data: " << cPTR << endl;
      else
        cout << "No data recieved." << endl;
    }
    ClosePort();
    return 0;
}

My proposal for read string function:

void ReadString(
  std::string& result,
  std::size_t& size)
{
  result.clear(); // If you need to keep track - don't clear

  BYTE byteIn;
  while (ReadByte(byteIn))
  {
    result.append(byteIn); // Maybe static_cast<char>(byteIn) required for BYTE to char
    size++;
  }
}

Now we can rewrite main as:

std::string buffer;
std::size_t length = 0;

while (true)
{
  ReadString(buffer, length);

  if(buffer.size())
    cout << "Scanned Data: " << buffer << endl;
  else
    cout << "No data recieved." << endl;

  // Some condition to break the cycle after 1Mb
  if (length > 1024 * 1024)
    break;
}