CODEWITHSUNDEEP
c++std
Stijn Frishert
Stijn Frishert

Reputation: 1583

How do I explicitly call the destructor of std iterators?

Given std::vector<A>::iterator and std::map<A, B>::iterator, how do I explicitly call their destructors? I do not know the actual names of these types, because the ::iterator member types are typedefs/aliases to implementation-specific classes.

I ask this question, because I am storing these iterators in an unrestricted c++ union and Visual Studio asks me to manually handle destruction. I could simply not call the destructor of the active element and assume iterators do not need clean-up, but that reeks of bad practice.

Upvotes: 0

Views: 1245

Answers (3)

eerorika
eerorika

Reputation: 238391

Like this:

// let iter be vector<int>::iterator to be destroyed
iter.std::vector<int>::iterator::~iterator();

I do not know the actual names of these types, because the ::iterator member types are typedefs/aliases to implementation-specific classes.

Doesn't matter. Type aliases are type names as well.

LLVM appears to have a bug with this: https://bugs.llvm.org//show_bug.cgi?id=12350

Until it is fixed, as a workaround, introduce a non-nested alias:

using iterator = std::vector<int>::iterator;
iterator it;
it.iterator::~iterator();

or refer to the type as template argument (this code is from the bug report): 

template <typename T>
inline void placement_delete(T *x) 
{
   // C++ lacks placement delete, so fake it with a function
   x->~T();
}

Upvotes: 4

n. m. could be an AI
n. m. could be an AI

Reputation: 120001

std::destroy_at(&iter);

std::destroy and friends are a C+17 feature. If your compiler lacks support it is trivial to implement yourself:

template <typename T>
void destroy_at(T* p) {
    p->~T();
}

Source.

Upvotes: 3

Mrnell
Mrnell

Reputation: 91

Most often iterator are nothing but pointer to already allocated memory. Unless the iterators are created using new

 typedef std::vector<A>::iterator VecIter;
 VecIter* iter= new VecIter;

there is no need to delete. If you are using new, then you can call delete explicitly for the iterator variable.

delete iter;

Upvotes: 0

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