Re: Customize operator new / delete

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 8 May 2011 07:38:53 -0700 (PDT)

Message-ID:

<78a4d447-9756-4dbc-ac6d-3513dbcd5031@l6g2000vbn.googlegroups.com>

On May 8, 3:11 am, Nephi Immortal <immortalne...@gmail.com> wrote:

I decide to customize my own operator new and operator delete
in the global scope. They are independent outside class as
long as they are not function members of any class.

Please confirm if my code is valid as C++ standard states. I
had examined across website via google search. I only find
user-defined classes, but not for global scope.

#include <stdio.h>
#include <malloc.h>

inline
void *operator new( size_t size ) { return malloc( size ); }

inline
void *operator new[]( size_t size ) { return malloc( size ); }

inline
void operator delete( void *pUserData ) { free( pUserData ); }

inline
void operator delete[]( void *pUserData ) { free( pUserData ); }

int main()
{
        char *p = new char[ 100 ];
        delete [] p;

        return 0;
}

The operator new do not meet the requirements set down in the
standard, particularly the post-condition that the returned
pointer is never null. You have to do something like:

    void operator new( size_t size )
    {
        void* result = malloc( size );
        if ( result == NULL ) {
            throw std::bad_alloc();
        }
        return result;
    }

Also, the implementations are not allowed to be inlined
(doubtlessly because the standard library is required to use
them if they are present, and the code in the standard library
has already been compiled expecting them not to be inlined).

--
James Kanze