CODEWITHSUNDEEP
c++boostbind
cprogrammer
cprogrammer

Reputation: 5675

boost::bind and delete

I need to map a delete ptrAddr; to a boost::function0 but i have some troubles doing that for delete. free works just fine. The issue appears to be std::ptr_fun(operator delete) but i can't figure how to make this work without writing a helper functor.

boost::function0<void> Function;
Function = boost::bind(std::ptr_fun(free), (void*)malloc_string);  //this works
Function = boost::bind(std::ptr_fun(operator delete), (void*)new_string);  //doesn't work
Function();  //call function

Upvotes: 3

Views: 2002

Answers (2)

Cat Plus Plus
Cat Plus Plus

Reputation: 129764

You can use delete_ptr from Boost.Lambda:

boost::bind(boost::delete_ptr(), new_string);

In C++11, you can use std::default_delete<T>:

std::bind(std::default_delete<decltype(new_string)>(), new_string);

Or just a lambda:

[new_string]() { delete new_string; }

Upvotes: 12

Kerrek SB
Kerrek SB

Reputation: 476970

delete p; is not a function call; it's an expression. What you want doesn't make sense.

There does exist a free function ::operator delete(), but that doesn't do what you think.

Look at the implementation of any standard library container (keyword: allocator), or perhaps std::unique_ptr, to see how one handles customizable object deletion.

The typical construction/destruction sequence broken down into pieces looks like this:

void * addr = ::operator new(sizeof(T));  // allocation

T * p = ::new (addr) T;                   // construction

p->~T();                                  // destruction

::operator delete(addr);                  // deallocation

The first to steps are morally equivalent to the expression T * p = new T;, while the last to correspond to delete p;. There is no way to call a constructor other than through a new expression, though; and you mustn't forget to invoke the destructor one way or another.

Upvotes: 4

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