Sessions on advanced C++ programming

A.4. Advanced memory handling

Topics

• Storage types in C++
  In C++ objects are mapped into the memory based on their storage types. Different storage types means different life rules.
• The new and delete operators
  New and delete expressions are calling new and delete operators. These functions form a complex set of operators.
• Overloading new and delete
  New and delete operators could be overloaded at two levels: as class member, we can define the allocation and deallocation process for objects for a certain class. At global level, we define these operations for all dynamic storage objects.
• Extra parameters for new and delete
  As we can overload new and delete operators at class or global level: we can provide extra parameters, for debug or other purposes. This example explain the details.
• Handling exceptions thrown by constructor
  When a constructor throw an exception under creation of object in the free space, the new expression catch this, and calls the according delete operator. In this example You can study this scenario.
• Resource allocation problems
  Memory leaks and other resource deallocation problems could be a major problem when exceptions are used in a C++ program. We see some typical dangerous situation and solution. Stroustrup suggested Resource allocation is initialisation strategy as the solution.
• The auto_ptr class
  This class is a wrapper for memory resource handling. Auto_ptr is the only smart pointer class in the C++ standard library and widely used in programs.
• Problems with auto_ptr
  The auto_ptr are not "silver bullets" for resource management. There are situations, when careless use of auto_ptr can cause memory leaks.
• Arrays are not polymorphic
  In object oriented programming, pointers to base could refer to derived objects. However arrays are very special in this case: arrays are not plymorphic.
• Array delete adapter
  The purpose of this code is to solve the array-problem of auto_ptr class. Arrays are not valid constructor parameters for auto_ptr, because auto_ptr destructor always calls delete, rather than delete[].
• Shared_ptr
  The shared_ptr and shared_arr classes are part of the tr1 library; the next extension of the C++ language.
• Example smart pointer
  This value_ptr class solves a special problem: when aggregation is implemented via pointers, special care must be taken on object ownership.