Resolving memory leaksCode:
1: // Listing 9.14
2: // Resolving memory leaks
3: #include <iostream.h>
4:
5: class SimpleCat
6: {
7: public:
8: SimpleCat (int age, int weight);
9: ~SimpleCat() {}
10: int GetAge() { return itsAge; }
11: int GetWeight() { return itsWeight; }
12:
13 private:
14: int itsAge;
15: int itsWeight;
16: };
17:
18: SimpleCat::SimpleCat(int age, int weight):
19: itsAge(age), itsWeight(weight) {}
20:
21: SimpleCat & TheFunction();
22:
23: int main()
24: {
25: SimpleCat & rCat = TheFunction();
26: int age = rCat.GetAge();
27: cout << "rCat is " << age << " years old!\n";
28: cout << "&rCat: " << &rCat << endl;
29: // How do you get rid of that memory?
30: SimpleCat * pCat = &rCat;
31: delete pCat;
32: // Uh oh, rCat now refers to ??
33: return 0;
34: }
35:
36: SimpleCat &TheFunction()
37: {
38: SimpleCat * pFrisky = new SimpleCat(5,9);
39: cout << "pFrisky: " << pFrisky << endl;
40: return *pFrisky;
41: }
Output: pFrisky: 0x2bf4
rCat is 5 years old!
&rCat: 0x2bf4
1: // Listing 9.14
2: // Resolving memory leaks
3: #include <iostream.h>
4:
5: class SimpleCat
6: {
7: public:
8: SimpleCat (int age, int weight);
9: ~SimpleCat() {}
10: int GetAge() { return itsAge; }
11: int GetWeight() { return itsWeight; }
12:
13 private:
14: int itsAge;
15: int itsWeight;
16: };
17:
18: SimpleCat::SimpleCat(int age, int weight):
19: itsAge(age), itsWeight(weight) {}
20:
21: SimpleCat & TheFunction();
22:
23: int main()
24: {
25: SimpleCat & rCat = TheFunction();
26: int age = rCat.GetAge();
27: cout << "rCat is " << age << " years old!\n";
28: cout << "&rCat: " << &rCat << endl;
29: // How do you get rid of that memory?
30: SimpleCat * pCat = &rCat;
31: delete pCat;
32: // Uh oh, rCat now refers to ??
33: return 0;
34: }
35:
36: SimpleCat &TheFunction()
37: {
38: SimpleCat * pFrisky = new SimpleCat(5,9);
39: cout << "pFrisky: " << pFrisky << endl;
40: return *pFrisky;
41: }
Output: pFrisky: 0x2bf4
rCat is 5 years old!
&rCat: 0x2bf4
Citat:
So far, so good. But how will that memory be freed? You can't call delete on the reference. One clever solution is to create another pointer and initialize it with the address obtained from rCat. This does delete the memory, and plugs the memory leak. One small problem, though: What is rCat referring to after line 31? As stated earlier, a reference must always alias an actual object; if it references a null object (as this does now), the program is invalid.
Citat:
There are actually three solutions to this problem. The first is to declare a SimpleCat object on line 25, and to return that cat from TheFunction by value. The second is to go ahead and declare the SimpleCat on the free store in TheFunction(), but have TheFunction() return a pointer to that memory. Then the calling function can delete the pointer when it is done.
The third workable solution, and the right one, is to declare the object in the calling function and then to pass it to TheFunction() by reference.
Moze li mi neko od specijalista ispisati to 3. i pravo resenje ?
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