CODEWITHSUNDEEP
c++destructordeclarationc++11
user751747
user751747

Reputation: 1093

A destructor Shall OR shall not be declared with a pointer ? in C++

In C++0x -n3290 Draft : they added in section :Destructors : 12.4/2nd point last line 

          **A destructor shall not be declared with a ref-qualifier.**

In c++03 Draft .... they didn't mention this point in destructors ?

my question is whether 

   *~S() ;   //this declaration is allowed or not according to the Standard's
   //**~S(); ***~S() ; etc...........

this type of declaration is allowed ? No where in the Draft he described about this ...Declaration?

In GCC 4.6.0,Sun/Oracle C++12.0 , --->this declaration is allowed int Comeau C/C++ -->not allowed

Upvotes: 8

Views: 254

Answers (3)

Johannes Schaub - litb
Johannes Schaub - litb

Reputation: 506925

The rule you are looking for is stated in the same paragraph, 12.4p2

A destructor takes no parameters, and no return type can be specified for it (not even void).

The phrase "no return type can be specified for it" also forbids "*", which is not immediately clear but can be seen by comparison with 12.3.2p1 (compare with this issue report):

... Such functions are called conversion functions. No return type can be specified.

That rule is what makes implementations forbid * operator int() { }. You can also argue with 12.4p1, although as that's phrased very general and is the first statement in the destructors section, I think the other statement above should be the primary argument

A special declarator syntax using an optional function-specifier (7.1.2) followed by ˜ followed by the destructor's class name followed by an empty parameter list is used to declare the destructor in a class definition.

As can be seen/read there is no mention of declarators such as * in that description, which shows the intent of the authors.

Upvotes: 1

David Rodríguez - dribeas
David Rodríguez - dribeas

Reputation: 208333

You have misunderstood what ref-qualifier means in the new standard. In the same way that you can provide a const qualifier to any member function in C++03, you can also add a ref-qualifier to a member function in C++0x. That modifier will affect the type of the implicit this argument to the function:

struct test {
   void f() const &&;  // implicit "this" in "f" is of type "test const &&"
};

In the same way that a destructor cannot be static, or const, or const volatile in C++03, it cannot take a ref-qualifier (& or &&) in C++0x. Of course this bit was not present in the former standard.

Upvotes: 7

Omnifarious
Omnifarious

Reputation: 56048

That doesn't look like it would ever be a legal function declaration of any kind, much less for a destructor. I'm not positive what that part of the standard is talking about, but I have a guess.

I suspect there is a qualifier saying that your function is being called on an rvalue reference. Something like this:

class A {
 public:
   void IAmAnRValue() &&;
};

I think the language in the standard is saying that this qualifier is not allowed on a destructor, much like having a trailing const would also be illegal.

And, on further investigation, my certainty of the correctness of my surmise goes up considerably. Here is the justification:

There it clearly states that functions may now have a 'ref-qualifier' after the 'cv-qualifer'. This means that a function declaration may now be followed by const & or const volatile && instead of just const. And the term used (ref-qualifier) is the same as the term used in the little bit of the standard you're quoting. And it makes sense for destructors to not be able to have one.

Upvotes: 10

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