深入理解C++中的new/delete和malloc/free动态内存管理及区别介绍

void *operator new(size_t); //allocate an object
void *operator delete(void *); //free an object

void *operator new[](size_t); //allocate an array
void *operator delete[](void *); //free an array

// new.cpp
#include <cstdlib>
#include <new>

_C_LIB_DECL
int __cdecl _callnewh(size_t size) _THROW1(_STD bad_alloc);
_END_C_LIB_DECL

void *__CRTDECL operator new(size_t size) _THROW1(_STD bad_alloc)
 { // try to allocate size bytes
 void *p;
 while ((p = malloc(size)) == 0)
  if (_callnewh(size) == 0)
  { // report no memory
   _THROW_NCEE(_XSTD bad_alloc, );
  }

 return (p);
 }

#include <cruntime.h>
#include <malloc.h>
#include <new.h>
#include <windows.h>
#include <rtcsup.h>

void operator delete( void * p )
{
 RTCCALLBACK(_RTC_Free_hook, (p, 0));

 free( p );
}

#include <new>

void *__CRTDECL operator new[](size_t count) _THROW1(std::bad_alloc)
	{	// try to allocate count bytes for an array
	return (operator new(count));
	}

#ifdef CRTDLL
#undef CRTDLL
#endif

#ifdef MRTDLL
#undef MRTDLL
#endif

#define _USE_ANSI_CPP // suppress defaultlib directive for Std C++ Lib
#include <new>

extern void __CRTDECL operator delete[](void *ptr) _THROW0();

void __CRTDECL operator delete[](void *ptr,
	const std::nothrow_t&) _THROW0()
	{	// free an allocated object
	operator delete[](ptr);
	}

new(int size) --> operator new() --> malloc() --> constructor function --> return ptr

delete ptr --> destructor function --> operator delete() --> free

new[count] --> operator new[]() --> operator new() --> malloc() --> constructor function --> return ptr

delete[] ptr --> destructor function --> operator delete[]() --> operator delete() --> free