cpp-variable-lifetime

时间:2022-08-13 08:26:21
#include <cstdio>
#include <iostream>
using namespace std;

class TmpClass;
void FuncScopeTmpClass(TmpClass s);

class TmpClass{
public:
    TmpClass():ident(i--){ printf("%2d ++\n", ident); }
    ~TmpClass() { printf("%2d --\n\n", ident); }
    int tick() { printf("%2d ||\n", ident); return i; }
private:
    int ident;
    static int i;
    friend void FuncScopeTmpClass(TmpClass s);
};

int TmpClass::i = 20; 

TmpClass GetTempClass() { return TmpClass(); } 

void FuncScope(int s) { printf("%2d >>\n", s); }
void FuncScopeTmpClass(TmpClass s) { printf("%2d <<\n", s.ident); }

int main() {
    while(GetTempClass().tick()) {
        TmpClass a, b;
        GetTempClass(), GetTempClass(), FuncScope ( GetTempClass().tick() );
        FuncScope ( GetTempClass().tick() ), GetTempClass();
        FuncScope ( GetTempClass().tick() );
        FuncScopeTmpClass ( (GetTempClass(), GetTempClass(), GetTempClass()));
        break;
    }; return 0;
}
/* standard output
20 ++
20 ||
20 --

19 ++
18 ++
17 ++
16 ++
15 ++
15 ||
14 >>
15 --

16 --

17 --

14 ++
14 ||
13 >>
13 ++
13 --

14 --

12 ++
12 ||
11 >>
12 --

11 ++
10 ++
 9 ++
 9 <<
 9 --

10 --

11 --

18 --

19 --
*/