ITEM 51: ADHERE TO CONVENTION WHEN

WRITING NEW AND DELETE

By Renan Campos

OVERVIEW When to overload new/delete and why Requirements of the implementing

“new” Implementing “array new” Implementing the “delete” operator Summary Example Code Questions

WHEN AND WHY (ITEM 50) To detect usage errors To collect statistics about the use of

dynamically allocated memory To increase the speed of allocation and

deallocation To reduce the space overhead of default

memory management To componsate for suboptimal alignment in

the default allocation To cluster related objects near one another To obtain unconventional behavior

IMPLEMENTING NEWThe new operator requires:1. The right return value2. Calling the new-handling function

when insufficient memory is available3. Being prepared to cope with requests

for no memory4. Avoiding hiding the normal form of

new (See item 52)5. Handle inherited classes

IMPLEMENTING NEW[]

Just allocate a chunk of raw memory.

IMPLEMENTING DELETEvoid operator delete( void* rawMem ) throw() {

if ( rawMem == 0 ) return ;

// deallocate the memory pointed

}

SUMMARYFor new: Operator new should contain an infinite loop

trying to allocate memory. New_handler should be called if memory

request failed. Class-specific versions should handle

requests for larger blocks than expected.For delete: Operator delete should do nothing if given a

null pointer. Class-specific versions should handle

requests for larger blocks than expected.

SAMPLE CODE

QUESTIONS?