相关疑难解决方法(0)

我想知道编译器在哪一点为块内的局部变量分配存储空间.goto和switch如何跳过构造函数？:

class Tree {/*...*/}
...
void foo (int i){
if (i < 10) goto label; //illegal: cannot jump past a ctor
 Tree t (45);
 label: 
   switch (i){
      case 1:
            Tree t2 (45);
            break;
      case 2: //illegal: cannot jump past ctor 
            Tree t3 (45);
            break;
   }
}

虽然上面的代码不适用于用户定义的对象,但如果我用内置对象替换它们,它就可以工作.这是为什么？

编辑:内置对象,如int,char等.我得到的错误(在ubuntu上的g ++ 4.5):

jumpPastConstructor.c++: In function ‘void foo(int)’:
jumpPastConstructor.c++:26:3: error: jump to label ‘label’
jumpPastConstructor.c++:24:20: error:   from here
jumpPastConstructor.c++:25:10: error:   crosses initialization of ‘Tree t’
jumpPastConstructor.c++:31:16: error: jump to case label
jumpPastConstructor.c++:29:25: error: …