According to Herb Sutter the code below wouldn't compile. See this site http://www.gotw.ca/gotw/066.htm from where I've extracted the following text, regarding function-try-blocks
:
Toward Some Morals
Incidentally, this also means that the only (repeat only) possible use for a constructor function-try-block is to translate an exception thrown from a base or member subobject. That's Moral #1. Next, Moral #2 says that destructor function-try-blocks are entirely usele--
"--But wait!" I hear someone interrupting from the middle of the room. "I don't agree with Moral #1. I can think of another possible use for constructor function-try-blocks, namely to free resources allocated in the initializer list or in the constructor body!"
Sorry, nope. After all, remember that once you get into your constructor try-block's handler, any local variables in the constructor body are also already out of scope, and you are guaranteed that no base subobjects or member objects exist any more, period. You can't even refer to their names. Either the parts of your object were never constructed, or those that were constructed have already been destroyed. So you can't be cleaning up anything that relies on referring to a base or member of the class (and anyway, that's what the base and member destructors are for, right?).
Assuming this quote, the following code should not compile, as the object cat
has already been destructed by the time the process runs into the catch
clause. But it does, at least with VSC2008.
class Cat
{
public:
Cat() { cout << "Cat()" << endl; }
~Cat() { cout << "~Cat()" << endl; }
};
class Dog
{
public:
Dog() { cout << "Dog()" << endl; throw 1; }
~Dog() { cout << "~Dog()" << endl; }
};
class UseResources
{
class Cat *cat;
class Dog dog;
public:
UseResources();
~UseResources() { delete cat; cat = NULL; cout << "~UseResources()" << endl; }
};
UseResources::UseResources() try : cat(new Cat), dog() { cout << "UseResources()" << endl; } catch(...)
{
delete cat;
throw;
}
I don't think Herb Sutter is actually saying that it won't compile. He is just explaining the consequences of what the standard has to say about the situation (15.3.10):