constructor - Storage allocation of local variables inside a block in c++ -

i want know @ point compiler allocates storage local variables inside block. how goto , switch jump past constructor? :

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

while above code not work user-defined objects works if replace them built-in objects. why that?

edit: built in objects int, char, etc. errors (g++ 4.5 on ubuntu):

jumppastconstructor.c++: in function ‘void foo(int)’: jumppastconstructor.c++:26:3: error: jump label ‘label’ jumppastconstructor.c++:24:20: error:   here jumppastconstructor.c++:25:10: error:   crosses initialization of ‘tree t’ jumppastconstructor.c++:31:16: error: jump case label jumppastconstructor.c++:29:25: error:   crosses initialization of ‘tree t2’ 

6.7/3:

it possible transfer block, not in way bypasses declarations initialization. program jumps point local variable automatic storage duration not in scope point in scope ill-formed unless variable has pod type (3.9) , declared without initializer (8.5).

what matters not when storage allocated, when constructor called. goto jumped past constructor problem, why it's banned. (pod types no initialiser don't need construction, they're allowed.)