vc申请内存结构

最新推荐文章于 2023-10-09 14:20:32 发布

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最新推荐文章于 2023-10-09 14:20:32 发布

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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 4
typedef 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;