Exception question

[junw2000@gmail.com]

class A
{
public:
A() { p_a = new int;}
~A() { delete p_a; } //Line1
private:
int *p_a;
}

void f()
{
try
{
A a1;
cout << "In f()" << endl;
g(); //Line2
A a2;
}
catch()
{
cout << "In catch" << endl;
}
}

void g()
{
cout << "In g()" << endl;
throw; //Line3
}

When an exception is thrown at Line3 in g(), stack will unwind at
Line2 in f(). When a1 is destructed, will Line1 be excecuted so that
p_a is deleted? How about a2?

Thanks.






}

[Paavo Helde]

Re: Exception question

junw2000@gmail. com kirjutas:

class A
{
public:
A() { p_a = new int;}
~A() { delete p_a; } //Line1
private:
int *p_a;
}
>

missing ;

void f()
{
try
{
A a1;
cout << "In f()" << endl;
g(); //Line2
A a2;
}
catch()

You probably meant "catch(...) " here.

{
cout << "In catch" << endl;
}
}
>
void g()
{
cout << "In g()" << endl;
throw; //Line3

You probably meant "throw 42;" here, throw without an argument can be
used only from inside a catch handler.

}
>
When an exception is thrown at Line3 in g(), stack will unwind at
Line2 in f(). When a1 is destructed, will Line1 be excecuted so that
p_a is deleted? How about a2?
>

Yes, the language is designed so that it would be possible to write
exception-safe code. a1 is destructed properly and a2 never gets created.

hth
Paavo

[Salt_Peter]

Re: Exception question

On Aug 6, 1:52 am, junw2...@gmail. com wrote:

class A
{
public:
A() { p_a = new int;}
~A() { delete p_a; } //Line1
private:
int *p_a;
>
}
>
void f()
{
try
{
A a1;
cout << "In f()" << endl;
g(); //Line2
A a2;
}
catch()
{
cout << "In catch" << endl;
}
>
}
>
void g()
{
cout << "In g()" << endl;
throw; //Line3
>
}
>
When an exception is thrown at Line3 in g(), stack will unwind at
Line2 in f(). When a1 is destructed, will Line1 be excecuted so that
p_a is deleted? How about a2?
>
Thanks.
>
}

When in doubt, prove it:

#include <iostream>

class A
{
int* p_a;
public:
A() : p_a(new int) { std::cout << "A()\n"; }
~A()
{
delete p_a;
std::cout << "~A()\n";
}
};

void g()
{
std::cout << "In g()" << std::endl;
throw 1; //Line3
}

void f()
{
try
{
A a1;
std::cout << "In f()" << std::endl;
g(); //Line2
A a2;
}
catch(...)
{
std::cout << "In catch" << std::endl;
}
}

int main()
{
f();
}

/*
A()
In f()
In g()
~A()
In catch
*/