Using boost::shared_ptr with WSACleanup

Question

I would like to use a boost::shared_ptr in order for WSACleanup() to be called when my function goes out of scope, like this:

void DoSomething() {
    WSAStartup(...);
    boost::shared_ptr<void> WSACleaner(static_cast<void*>(0), WSACleanup);
}

This does not compile,

Error 1 error C2197: 'int (__stdcall *)(void)' : too many arguments for call C:\projects\svn-5.3\ESA\Common\include\boost\detail\shared_count.hpp 116

any thoughts?

MSalters · Accepted Answer · 2011-10-11T12:25:30.073

1

From the docs: "The expression d(p) must be well-formed" (i.e. WSACleanup(static_cast<void*>(0) must be well-formed.)

One possible solution:

boost::shared_ptr<void> WSACleaner(static_cast<void*>(0),
                                   [](void* dummy){WSACleanup();});

edited Oct 11 '11 at 12:25

answered Oct 11 '11 at 12:14

MSalters

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this looks elegant, could you please elaborate on the syntax of `[](void* dummy){WSACleanup();}` – tsotso Oct 11 '11 at 12:46
@tsotso: This is not a site for teaching the basics of C++11. – Lightness Races in Orbit Oct 11 '11 at 12:48
1

@tsotso: If you want to google it, it's called a "lambda expression". It allows you to write a function whereever you can use a function pointer – MSalters Oct 11 '11 at 12:57
2

@TomalakGeret'kal A simple link to [Lambda functions](http://en.wikipedia.org/wiki/C%2B%2B11#Lambda_functions_and_expressions) would have been much more helpful than your inaccurate statement – tsotso Oct 11 '11 at 12:58
@tsotso: In what way was it inaccurate? – Lightness Races in Orbit Oct 11 '11 at 12:59
1

BTW standard alternative would be `std::unique_ptr` - you need to pass the type of the deleter. – MSalters Oct 11 '11 at 13:03
@MSalters: thanks, any way to achieve the same without C++0x syntax? boost? – tsotso Oct 11 '11 at 13:09
@tsotso: For a 20th century solution ;) see rodrigo's comment to jcalvosa answer. – MSalters Oct 11 '11 at 13:15

score 1 · Answer 2 · answered Oct 11 '11 at 12:17

1

You can create a class Awhich destructor invoques WSACleanup and instance of shared_ptr with it:

class A
{
    public:
        ~A() { WSACleanup(...); }
}

....

void DoSomething() {
    WSAStartup(...);
    boost::shared_ptr<A> x(new A);
}

answered Oct 11 '11 at 12:17

Tio Pepe

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But then, you can just create a local variable of that type. And now that you are on it, you can call `WSAStartup` from the constructor. – rodrigo Oct 11 '11 at 12:27
@rodrigo yes you are right, but can use it wherever you want in other scope of program. – Tio Pepe Oct 11 '11 at 12:30
1

Using a class with ctor and dtor is the far cleaner solution. It's also easily extended to situations where you might have multiple sections of code that require network connections, potentially overlapping in time. Just use a private static counter to keep track of the ctor-dtor balance. – MSalters Oct 11 '11 at 12:34

Using boost::shared_ptr with WSACleanup

2 Answers2