1、看看Qt源码中如何定义QT_TRY和QT_CATCH的： 

 1 inline void qt_noop(void) {}
 2  
 3 /* These wrap try/catch so we can switch off exceptions later.
 4    Beware - do not use more than one QT_CATCH per QT_TRY, and do not use
 5    the exception instance in the catch block.
 6    If you can't live with those constraints, don't use these macros.
 7    Use the QT_NO_EXCEPTIONS macro to protect your code instead.
 8 */
 9  
10 #ifdef QT_BOOTSTRAPPED
11 #  define QT_NO_EXCEPTIONS
12 #endif
13 #if !defined(QT_NO_EXCEPTIONS) && defined(Q_CC_GNU) && !defined (__EXCEPTIONS) && !defined(Q_MOC_RUN)
14 #  define QT_NO_EXCEPTIONS
15 #endif
16  
17 #ifdef QT_NO_EXCEPTIONS
18 #  define QT_TRY if (true)
19 #  define QT_CATCH(A) else
20 #  define QT_THROW(A) qt_noop()
21 #  define QT_RETHROW qt_noop()
22 #else
23 #  define QT_TRY try
24 #  define QT_CATCH(A) catch (A)
25 #  define QT_THROW(A) throw A
26 #  define QT_RETHROW throw
27 #endif

2、我们来使用下QT的异常处理

1 // 在.pro 中增加如下配置 ==》 Qt默认是不开启异常的
2 CONFIG += exception

 1 // main.cpp
 2  
 3 enum Except{ EXCEP_ZERO,EXCEP_ONE};
 4  
 5  void func(int a){
 6      if(a ==0) throw (EXCEP_ZERO); // 抛出异常
 7  }
 8  
 9 int main(int argc, char *argv[])
10 {
11     QApplication a(argc, argv);
12  
13     QT_TRY {
14         func(1);
15     } QT_CATCH(Except ex) {
16         if(ex == EXCEP_ZERO) QT_RETHROW;
17     }
18  
19  
20  
21     Widget w;
22     w.show();
23     return a.exec();
24 }