Why is delete[] not equivalent to calling delete for each element in C++?

c++ delete vs delete[]
delete[] c++
delete function in c
c++ delete object
c++ delete array element
c delete element from dynamic array
c++ delete vs free
c++ delete pointer

Assuming I created an array in the heap:

int* a = new int[10];

Why is this:

for(int i = 0; i < 10; i++) {
        delete (a + i);
}

not equivalent to delete[] a;? Attempting to call delete for any pointer to an element in a results in an memory access violation.

What excactly is the difference?

The pointer you give to delete has to be a pointer that was returned by new. Furthermore, if you use new[] to allocate the object, you have to use delete[] to delete it.

In many implementations, the metadata that holds information about an allocation (e.g. the size of the allocation) is stored in the memory just before the allocation. So when you pass a pointer to delete, it looks in the preceding memory locations to find this information. When you allocate an array, there's only one of these metadata blocks for the entire allocation. If you try to delete an element inside the array, there won't be any metadata before it, so it won't know how much memory to free.

delete() in C++, delete() in C++. Delete is an operator that is used to destroy array and non-array(​pointer) objects Deleting Array Objects: We delete an array using [] brackets. Minimum cells to be flipped to get a 2*2 submatrix with equal elements in C++ STL with Examples · How to call some function before main() function in C++?  Delete is an operator that is used to destroy array and non-array(pointer) objects which are created by new expression. Delete can be used by either using Delete operator or Delete [ ] operator New operator is used for dynamic memory allocation which puts variables on heap memory.

No. Array-type storage is what amounts to contains one object , for which storage was allocated and it should be deallocated accordingly.

From 8.3.4 New

If the allocated type is a non-array type, the allocation function’s name is operator new and the deallocation function’s name is operator delete. If the allocated type is an array type, the allocation function’s name is operator new[] and the deallocation function’s name is operator delete[].

Pointer returned by new expression should be deallocated by delete. new[] expression returns pointer to first element of array and to deallocate array you should use only delete[] operator. Other combinations yield UB and the use delete on element of array is UB.

operator delete[] - C++ Reference, (1) ordinary delete: Deallocates the memory block pointed to by ptr (if not null), releasing the But in C++, delete[] is an operator with a very specific behavior: An for each element in the array (if these are of a class type), and then calls an array Calls to allocation and deallocation functions that reuse the same unit of​  But in C++, delete[] is an operator with a very specific behavior: An expression with the delete[] operator, first calls the appropriate destructors for each element in the array (if these are of a class type), and then calls an array deallocation function.

new int[10] allocates one block of memory with enough room for ten objects of type int. When you're done with that memory block you need to release it; you do that with delete [], which tells the runtime system that you're finished with that one block of memory.

That's the simple case. When you allocate memory for a type that has a non-trivial destructor, the compiler has to generate code to destroy each of the array elements. In that case, new T[10] allocates one block of memory with enough room for ten objects of type T, and it creates those ten objects using the default constructor. When you're done what that memory block you need to release it; you do that with delete [], which calls the destructor for each of the ten elements, then tells the runtime system that you're finished with that one block of memory.

Memory Management, C++ FAQ, Can I drop the [] when delete ing an array of some built-in type ( char , int , etc)? Besides all that, the heap that new uses may not be the same as the heap that In C++, if the runtime system cannot allocate sizeof(Fred) bytes of memory so the compiler will call the appropriate destructors for all elements in the array. The delete operator has a result of type void and therefore does not return a value. For example: CDialog* MyDialog = new CDialog; // use MyDialog delete MyDialog; Using delete on a pointer to an object not allocated with new gives unpredictable results. You can, however, use delete on a pointer with the value 0.

operator delete, operator delete[], The replaceable deallocation functions (1-12) are implicitly declared in each translation unit even if the <new> header is not included. These  Start studying bcis 3630 chapter 7. Learn vocabulary, terms, and more with flashcards, games, and other study tools.

6.9, int *ptr{ new int }; // dynamically allocate an integer and assign the address to ptr For single variables, this is done via the scalar (non-array) form of the delete First, try to avoid having multiple pointers point at the same piece of dynamic memory. `malloc` allocates memory but doesn't initialize anything and doesn't call  3. after completing a particular recursive call, control goes back to the calling environment, which is the previous call. the current (recursive) call must execute completely before control goes back to the previous call. the execution in the previous call begins from the point immediately following the recursive call.

Can I free() pointers allocated with new? Can I delete pointers , 16.28, Where can I get more info on garbage collectors for C++? Sometimes people say, "But I'm just working with an array of char." Nonetheless do not mix malloc() and delete on the same pointer, or new and free() on the same pointer! If you allocated via p = new char[n], you must use delete[] p; you must not use free(​p). The range used is [first,last), which contains all the elements between first and last, including the element pointed by first but not the element pointed by last. fn Unary function that accepts an element in the range as argument. This can either be a function pointer or a move constructible function object. Its return value, if any, is ignored.

Comments
  • show the whole code
  • Because that's the way it works.
  • The pointer you give to delete has to be a pointer that was returned by new. You only got a, not a+1, a+2, etc.
  • @Swift It's undefined behavior to try to delete a pointer that was not returned by new.
  • @Barmar UB here is actually use delete on pointer returned by new[].