blocks, storage and objects

[mickey]

Hello, I have this problem. I read the storage for a block (and thus for all "the things" inside it) are allocate after "{" of the block. Then I found this code below (thinking in c++ page 292 webEdition) that explain how to don't use jump and case (in such case). I uderstand:
1. the goto can't be there (otherwise I allocate storage but I could "not create" and initialize my1
2. Why is it ok? ( there is possible to skip My my2; )
3. With or without "case 2" My my3 are always skipped (then?)

I hope you'll understanding my troubles; thanks.

class My {
public:
	My();
};
 
My::My() {}
 
void p292 (int i) {
	if (i < 10) {
		//goto jump1;    // I understand
	}
	My my1;
jump1:
	switch (i) {
		case 10:
			My my2;  // I don't understand
			break;
		//case 2: //with this it doesn't compile
			My my3; // (I don't understand)^2
			break;
	};
}

class My {
public:
	My();
};

My::My() {}

void p292 (int i) {
	if (i < 10) {
		//goto jump1;    // I understand
	}
	My my1;
jump1:
	switch (i) {
		case 10:
			My my2;  // I don't understand
			break;
		//case 2: //with this it doesn't compile
			My my3; // (I don't understand)^2
			break;
	};
}

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[fullmetalcoder]

To allocate local variables within a switch/case block you need to use brackets :

switch ( i )
{
    case 0 :
    {
         bool compilerError = false;
         break;
    }
 
   default :
         bool compilerError = true;
         break;
}

switch ( i )
{
    case 0 :
    {
         bool compilerError = false;
         break;
    }
     
   default :
         bool compilerError = true;
         break;
}

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[mickey]

the question wasn't that. (in fact compiler gets errors like " initialization is skipped by 'jump/case 2'....

[wysota]

You can rewrite the switch as:

{
  if(i==10) goto _l10; else if(i==2) goto _l2; else goto _lafter;
_l10:
  My my2;
  goto _lafter;
_l2:
  My my3;
  goto _lafter;
_lafter:
}

{
  if(i==10) goto _l10; else if(i==2) goto _l2; else goto _lafter;
_l10:
  My my2;
  goto _lafter;
_l2:
  My my3;
  goto _lafter;
_lafter:
}

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It should become clear now why some constructions are invalid and others not.

[mickey]

sorry but isn't clear what am I was wondering in post#1...

[wysota]

Compare your code and mine. If you look at my code after reading what you wrote regarding "goto", you should understand why compiler denies such "case" constructions.

[mickey]

Compare your code and mine. If you look at my code after reading what you wrote regarding "goto", you should understand why compiler denies such "case" constructions.

Sorry please....
(refer post#1) "jump" gets only a "warning". The presence of "case 2" gets an "error" (reason?). Then: compiler (with case 2) says: "initialization of my2 is skipped by case 2". I say: if i was 2, then "My my2" could be skipped.
1. why if I comment line "case 2" it don't get error? (running program, could be skipped My my2 (as before) and ALWAYS "MY my3" will be skipped.
2. Anyway: why compiler doens't get even a message as "initialization of my3 is skipped by case 10" ?
Maybe I don't know when is the initialization (or similar)....