activeItem = menuItems.begin(); // where activeItem is a vector iterator and a member variable of Menu and menuItems is a vector
[SOLVED] Assigning Iterator to Iterator
Author
I'm getting a debug assertion "vector iterators incompatible" so I traced it down.
I discovered that when I step over in this line
activeItem has a member (error) with value 0
Then I went over to the constructor (activeItem is a member variable of Menu), activeItem still had a member (error) with value 0. What's up with this? Are iterators required to be initialized or something?
[Edited by - Sanctux on December 24, 2009 2:33:42 AM]
While you say they are vector iterators, that is not enough to fully specify their type. vector<int>::iterator and vector<double>::iterator are both "vector iterators" but it doesn't mean they are compatible.
Author
Thanks for the reply, stonemetal.
Here's what I have:
I'm pretty sure they're the same type of iterators; unless I got lost in the typedefs. [totally]
Here's what I have:
typedef std::pair<int, MenuItem> MenuPair;typedef std::vector<MenuPair> MenuVec;typedef MenuVec::iterator MenuIter;class Menu{// ...private:// ... MenuVec menuItems; MenuIter activeItem;// ...};I'm pretty sure they're the same type of iterators; unless I got lost in the typedefs. [totally]
What is the condition that's triggering that assert? That will tell us why it thinks they are "incompatible"...
Could be a bug in the library
Is the function this code is being run in a const member function?
If so that would cause the const version of menuItems.begin() to be called, returning a const_iterator, not an iterator.
If so that would cause the const version of menuItems.begin() to be called, returning a const_iterator, not an iterator.
I mean the library code that trips that assert, likely somewhere in <vector> - callstack should tell you
Author
Quote:Original post by diablos_blade
Is the function this code is being run in a const member function?
Nope.
Here's the source of the assertion (in vector):
void _Compat(const _Myt& _Right) const { // test for compatible iterator pair if (this->_Mycont == 0 || this->_Mycont != _Right._Mycont) { _DEBUG_ERROR("vector iterators incompatible"); _SCL_SECURE_INVALID_ARGUMENT; } }In case it might help, further up the call stack:
bool operator==(const _Myt& _Right) const { // test for iterator equality #if _HAS_ITERATOR_DEBUGGING _Compat(_Right); #else _SCL_SECURE_VALIDATE(this->_Has_container() && this->_Same_container(_Right)); #endif /* _HAS_ITERATOR_DEBUGGING */ return (_Myptr == _Right._Myptr); }Thanks for the replies! [smile]
Was one of the iterators assigned to a different container previously?
What is the value of _Mycont for each iterator when it asserts?
Can you check operator= for the iterator to make sure it assigns the _Mycont member?
What is the value of _Mycont for each iterator when it asserts?
Can you check operator= for the iterator to make sure it assigns the _Mycont member?
Author
Quote:Original post by RDragon1
Was one of the iterators assigned to a different container previously?
What is the value of _Mycont for each iterator when it asserts?
Can you check operator= for the iterator to make sure it assigns the _Mycont member?
1. Well, the only time I did anything else with activeItem was here:
activeItem = menuItems.begin();2. this->_Mycont has value 0x00000000 and its member _Myfirstiter has CXX0030: Error: expression cannot be evaluated. _Right._Mycont has value 0x056a4844.
3. Here's operator=:
_Myt& operator=(const _Myt& _Right) { // assign _Right if (this != &_Right) { // worth doing #if _HAS_ITERATOR_DEBUGGING this->_Orphan_all(); #endif /* _HAS_ITERATOR_DEBUGGING */ if (_Right.size() == 0) clear(); // new sequence empty, erase existing sequence else if (_Right.size() <= size()) { // enough elements, copy new and destroy old pointer _Ptr = _STDEXT unchecked_copy(_Right._Myfirst, _Right._Mylast, _Myfirst); // copy new _Destroy(_Ptr, _Mylast); // destroy old _Mylast = _Myfirst + _Right.size(); } else if (_Right.size() <= capacity()) { // enough room, copy and construct new pointer _Ptr = _Right._Myfirst + size(); _STDEXT unchecked_copy(_Right._Myfirst, _Ptr, _Myfirst); _Mylast = _Ucopy(_Ptr, _Right._Mylast, _Mylast); } else { // not enough room, allocate new array and construct new if (_Myfirst != 0) { // discard old array _Destroy(_Myfirst, _Mylast); this->_Alval.deallocate(_Myfirst, _Myend - _Myfirst); } if (_Buy(_Right.size())) _Mylast = _Ucopy(_Right._Myfirst, _Right._Mylast, _Myfirst); } } return (*this); }and
_Mytype& operator=(const _Mytype& _Right) { // assign _Vb_reference _Right to bit return (*this = bool(_Right)); } _Mytype& operator=(bool _Val) { // assign _Val to bit if (_Val) *_Getptr() |= _Mask(); else *_Getptr() &= ~_Mask(); return (*this); }Thanks!
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