new-operator

Given a class: class clsPerson { public int x, y; } Is there some way to create an array of these classes with each element initialized to a (default) constructed instance, without doing it manually in a for loop like: clsPerson[] objArr = new clsPerson[1000]; for (int i = 0; i < 1000; ++i) objArr[i] = new clsPerson(); Can I shorten the declaration and instantiation of an array of N objects? You must invoke the constructor for each item. There is no way to allocate an array and invoke your class constructors on the items without constructing each item. You could shorten it (a tiny bit) from a

This question already has answers here : Closed 7 years ago . Possible Duplicate: How do you realloc in C++? I know that C++ arrays can be reallocated (expanded) using realloc() if memory has been allocated via malloc() or calloc() . My question is, how can I expand an array in C++ whose memory has been allocated via the new operator? You can't - that's why in C++ you use std::vector<> . If you wanted to do this, you'd have to allocate a new array (via new ), then copy the old items across ( std::copy for example), then delete[] the previous array. Just use std::vector - let it do all that

I defined a class foo as follows: class foo { private: static int objcnt; public: foo() { if(objcnt==8) throw outOfMemory("No more space!"); else objcnt++; } class outOfMemory { public: outOfMemory(char* msg) { cout << msg << endl;} }; ~foo() { cout << "Deleting foo." << endl; objcnt--;} }; int foo::objcnt = 0; And here's the main function: int main() { try { foo* p = new foo[3]; cout << "p in try " << p << endl; foo* q = new foo[7]; }catch(foo::outOfMemory& o) { cout << "Out-of-memory Exception Caught." << endl; } } It is obvious that the line "foo* q = new foo[7];" only creates 5 objects

A lot of classes has assignment operator (operator=) the same code as in destructor and than very similar code of copy constructor. So is it good idea to implement the assignment in such way? Point& operator=(const Point& point) { if(&point != this) { //Call the destructor this->~Point(); //Make the placement new //Assignment is made because some compilers optimise such code as just // new Point; Point* p_n = new (this) Point(point); //We where placing in this place so pointers should be equal assert(p_n == this); } return *this; } Fred Larson Herb Sutter has addressed this in one of his GotW

Possible Duplicate: C++'s “placement new” in the below code what does Line 3 represents, is it the way of typecasting? or what void someCode() { char memory[sizeof(Fred)]; // Line #1 void* place = memory; // Line #2 Fred* f = new(place) Fred(); // Line #3 // The pointers f and place will be equal ... } This is a typical usage of Placement new . It allows you to allocate memory and then construct objects at that particular memory location. Line #3 essentially just calls the constructor Fred::Fred() . The this pointer in the Fred constructor will be equal to place . The returned pointer f will