/home/idiao123/ceshi/mainwindow.cpp:17: error: 'open_buzzer' was not declared in this scope
open_buzzer();
^
/home/idiao123/ceshi/mainwindow.cpp:21: error: 'close_buzzer' was not declared in this scope
close_buzzer();
^
/home/idiao123/ceshi/mainwindow.cpp:44: error: 'set_buzzer_freq' was not declared in this scope
set_buzzer_freq(freq);
^
/home/idiao123/ceshi/mainwindow.cpp:-1: In member function 'void MainWindow::playBuzzer(int, int)':
/home/idiao123/ceshi/mainwindow.cpp:45: error: no matching function for call to 'QTimer::singleShot(int&, MainWindow*, MainWindow::playBuzzer(int, int)::<lambda()>)'
QTimer::singleShot(duration, this, []() { stop_buzzer(); });
^
