c++ - 我有 1 处内存泄漏，无法释放

Question

    #define _CRT_SECURE_NO_WARNINGS 
    #include < stdio.h >
    #include < stdlib.h >
    #include < string.h >
    #include < crtdbg.h >
    #define _CRTDBG_MAP_ALLOC

    enum {
        RUNNING = 1
    };

    struct Point {
        int x, y;
    };

    struct Line {
        Point start;
        Point end;
    };

    struct GraphicElement {
        enum {
            SIZE = 256
        };
        unsigned int numLines; //number of lines
        Line * pLines; //plines points to start and end
        char name[SIZE];
    };

    typedef struct {
        unsigned int numGraphicElements;
        GraphicElement * pElements; //the head points to pLines
    }
    VectorGraphic;

    void InitVectorGraphic(VectorGraphic * );
    void AddGraphicElement(VectorGraphic * );
    void CleanUpVectorGraphic(VectorGraphic * );

    VectorGraphic Image;

    int main() {
        char response;
        InitVectorGraphic( & Image);

        _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);

        while (RUNNING) {
            printf("\nPlease select an option:\n");
            printf("1. Add a Graphic Element\n");
            printf("2. List the Graphic Elements\n");
            printf("q. Quit\n");
            printf("CHOICE: ");
            fflush(stdin);
            scanf("%c", & response);

            switch (response) {
                case '1':
                    AddGraphicElement( & Image);
                    break;
                case '2':
                    ReportVectorGraphic( & Image);
                    break;
                case 'q':
                    CleanUpVectorGraphic( & Image);
                    return 0;
                default:
                    printf("Please enter a valid option\n");
            }
            printf("\n");
        }
    }

    /*initialize the vectors, allocate memory*/
    void InitVectorGraphic(VectorGraphic * pImage) { //addres of pImage is passed in
        pImage - > pElements = (GraphicElement * ) malloc(sizeof(GraphicElement)); //pImage is now the addess of image
        pImage - > numGraphicElements = 0;
    }



    /*add values into the vectors list.*/
    void AddGraphicElement(VectorGraphic * pImage) {
        struct GraphicElement * pElements;
        struct GraphicElement * pSecond;
        struct Point point;
        struct Line * line;
        unsigned int numLines;
        char name[256];
        int x;
        int y;
        int i = 0;
        int count = 0;

        //allocate memory
        line = (struct Line * ) malloc(20 * sizeof(Line)); //allocate memory for line, in order to accsess Line struct values


     pElements = (GraphicElement * ) malloc(20 * sizeof(GraphicElement));
            printf("Please enter the name of the new GraphicElement(<256 characters): ");
            scanf("%s", name);
            strcpy(pElements - > name, name); //copy the elements name

            printf("How many lines are there in the  new GraphicElement? ");
            scanf("%u", & numLines);
            pElements - > numLines = numLines; //pass the number of lines indicated
            pImage - > pElements = pElements; //pass the number of lines indicated



        pImage - > pElements[pImage - > numGraphicElements] = * pElements;    //pass the elements into pImage
        pImage - > numGraphicElements++; //number of elements   

一旦我按 q 退出。该程序显示我有内存泄漏。检测到内存泄漏!转储对象 ->{69} 位于 0x00EF9880 的正常 block ，长度为 264 字节。数据:<> CD CD CD CD CD CD CD CD CD CD CD CD CD CD CD对象转储完成

    /*clear everything, no memory leaks*/
    void CleanUpVectorGraphic(VectorGraphic * pImage) {
        /* free all Lines pointers */
        for (int i = 0; i < pImage - > pElements - > numLines; i++) {
            free(pImage - > pElements[i].pLines);
        }
        pImage - > pElements - > numLines = 0;
        pImage - > numGraphicElements = 0;

        if (pImage != NULL) {
            free(pImage - > pElements);
        }
    }

基本上，我的程序会提示用户输入元素名称和元素数量。之后，我输入 start(x,y) 和 end(x,y) 的 int 值。之后我按 q 退出并退出程序。我已经通过调试器进行了调试，但没有弄清楚内存泄漏在哪里。我尝试了很多不同的策略，但都失败了。我怎样才能释放这个内存泄漏？

注意:此外，如果我添加第二个元素，内存泄漏也会重复。

Answer 1

从内存块的大小看来，您尝试释放的指向 GraphicElement 的指针并未指向任何内容

在使用、取消引用或释放原始指针之前始终检查它们:

void CleanUpVectorGraphic(VectorGraphic * pImage) {
    //always check input
    if(!pImage) {
         return;
    }
    /* free all Lines pointers */
    for (int i = 0; i < pImage->pElements->numLines; i++) {
        if(pImage->pElements && pImage->pElements[i] && pImage->pElements[i].pLines) {
            free(pImage->pElements[i].pLines);
        }
    }
    pImage->pElements->numLines = 0;
    pImage->numGraphicElements = 0;

    if (pImage != NULL) {
        free(pImage->pElements);
    }
}