operator new 与 operator delete

关于内存分配器的测试，首先是例子程序：

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

#if defined( USE_DL_MALLOC )
    extern "C" void * dlmalloc( size_t );
    extern "C" void dlfree( void * );
#   define MALLOC dlmalloc
#   define FREE dlfree
#else
#   define MALLOC malloc
#   define FREE free
#endif

struct Allocator
{
	static void * operator new ( size_t space_length )
	{
		printf( "acquare %u space\n" , space_length );
		return MALLOC( space_length );
	}

	static void operator delete ( void * space_pointer , size_t space_length )
	{
		printf( "release %u space %p\n" , space_length , space_pointer );
		FREE( space_pointer );
	}

	static void * operator new [ ] ( size_t space_length )
	{
		printf( "acquare %u array\n" , space_length );
		return MALLOC( space_length );
	}

	static void operator delete [ ] ( void * space_pointer , size_t space_length )
	{
		printf( "release %u array %p\n" , space_length , space_pointer );
		FREE( space_pointer );
	}
};

struct Matrix_1x4 : public Allocator
{
	int X01 , X02 , X03 , X04 ;
}; 

struct Matrix_4x4 : public Matrix_1x4
{
	int X11 , X12 , X13 , X14 ;
	int X21 , X22 , X23 , X24 ;
	int X31 , X32 , X33 , X34 ;
}; 

struct Matrix_1x3
{
	int X01 , X02 , X03 ;
};

struct Matrix_3x3 : public Matrix_1x3 , public Allocator
{
	int X11 , X12 , X13 ;
	int X21 , X22 , X23 ;
};

int main( int argc , char * argv[ ] )
{
	Matrix_1x4 * pArray1 = new Matrix_1x4[ 2 ];
	Matrix_4x4 * pArray2 = new Matrix_4x4[ 2 ];

	Matrix_1x3 * pArray3 = new Matrix_1x3[ 2 ];
	Matrix_3x3 * pArray4 = new Matrix_3x3[ 2 ];

	delete [ ] pArray1; delete [ ] pArray2; 
	delete [ ] pArray3; delete [ ] pArray4; 

	Matrix_1x4 * pMatrix1 = new Matrix_1x4;
	Matrix_4x4 * pMatrix2 = new Matrix_4x4;

	Matrix_1x3 * pMatrix3 = new Matrix_1x3;
	Matrix_3x3 * pMatrix4 = new Matrix_3x3;

	delete pMatrix1; delete pMatrix2; 
	delete pMatrix3; delete pMatrix4; 
}

将该文件命名为 demo.cpp ，如果采用系统默认的分配器，则使用下面的命令行编译：

cl demo.cpp

然后执行 demo.exe 就可以看到结果，如果要测试使用 Doug Lea 的内存分配器，则使用如下的命令行编译：

cl demo.cpp dlmalloc.c /DUSE_DL_MALLOC

运行的结果应该是一致的，同时从运行结果可以看出在执行 delete 或者 delete[] 时，系统给的大小，应该是对象的 sizeof 的结果，即使数组也是如此，因此在 delete[] 中给出的大小仅仅是一个对象的大小，而不是整个数据占用内存空间的真实大小；

关于 Doug Lea 的 malloc 实现可以从这里获得，或者直接使用 ftp://g.oswego.edu/pub/misc/malloc.c 进行下载。