operator delete is unique in being a non-member or static member function that is dynamically dispatched. A type with a virtual destructor performs the call to its own delete from the most derived destructor. struct abc { virtual ~abc() = 0; }; struct d : abc { operator delete() { std::cout << “goodbye\n”; } }; … Read more
Every use of new should be balanced by a delete, and every use of new[] should be balanced by delete[]. for(int i=0;i<N;i++) delete array[i]; delete[] array; That would be appropriate only if you initialized the array as: Objects **array = new Objects*[N]; for (int i = 0; i < N; i++) { array[i] = new … Read more
Base* p = new Base[n] creates an n-sized array of Base elements, of which p then points to the first element. Base* p = new Derived[n] however, creates an n-sized array of Derived elements. p then points to the Base subobject of the first element. p does not however refer to the first element of … Read more
This as written is legal. The cast back to MyCls* is critical. Without that, you will invoke undefined behavior–the MyCls destructor will not be called, and other problems may arise as well (such as a crash). You must cast back to the correct type. Also note that this can be complicated if multiple inheritance is … Read more
::operator delete[] is documented on cplusplus.com (which is sometimes frowned upon) as: operator delete[] can be called explicitly as a regular function, 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 … Read more
Is being able to access data from beyond the grave expected? This is technically known as Undefined Behavior. Don’t be surprised if it offers you a can of beer either.
You delete [] when you newed an array type, and delete when you didn’t. Examples: typedef int int_array[10]; int* a = new int; int* b = new int[10]; int* c = new int_array; delete a; delete[] b; delete[] c; // this is a must! even if the new-line didn’t use [].
If in fact your question really is “I have this trivial program, is it OK that I don’t free a few bytes before it exits?” the answer is yes, that’s fine. On any modern operating system that’s going to be just fine. And the program is trivial; it’s not like you’re going to be putting … Read more
According to C++14 [expr.delete]/7: If the value of the operand of the delete-expression is not a null pointer value, then: [ …omitted… ] Otherwise, it is unspecified whether the deallocation function will be called. So both compilers do comply with the standard, because it’s unspecified whether operator delete is called for deletion of a null … Read more
Whether this leads to a memory leak, wipes your hard disk, gets you pregnant, makes nasty Nasal Demons chasing you around your apartment, or lets everything work fine with no apparent problems, is undefined. It might be this way with one compiler, and change with another, change with a new compiler version, with each new … Read more