vc申请内存结构

申请的内存布局_CrtMemBlockHeader +申请的可用内存+nNoMansLandSize(4)字节

_CrtMemBlockHeader放置申请的信息，包括申请的内存大小，_CrtMemBlockHeader中的gap和结尾的nNoMansLandSize被初始化为_bNoMansLandFill(0xFD),可用内存被初始化为_bCleanLandFill(0xCD)

// 获取申请的内存大小，win32平台，其他同理，未测试#define nNoMansLandSize 4typedef struct _CrtMemBlockHeader{        struct _CrtMemBlockHeader * pBlockHeaderNext;        struct _CrtMemBlockHeader * pBlockHeaderPrev;        char *                      szFileName;        int                         nLine;#ifdef _WIN64        /* These items are reversed on Win64 to eliminate gaps in the struct         * and ensure that sizeof(struct)%16 == 0, so 16-byte alignment is         * maintained in the debug heap.         */        int                         nBlockUse;        size_t                      nDataSize;#else  /* _WIN64 */        size_t                      nDataSize;        int                         nBlockUse;#endif  /* _WIN64 */        long                        lRequest;        unsigned char               gap[nNoMansLandSize];        /* followed by:         *  unsigned char           data[nDataSize];         *  unsigned char           anotherGap[nNoMansLandSize];         */} _CrtMemBlockHeader;int mem_size = ((_CrtMemBlockHeader*)mPoints - 1)->nDataSize;