c - 结构处理和结构数组

Question

我正在编写代码来存储文本文件中的数据。代码可以编译，但它似乎停止在 ReadPanelBlock 函数的 for 循环中运行。它的结构如下:CHBStructure 包含 CHBPanels，后者包含 CHBOpenings。创建这些函数是为了从输入文本文件中读取，我将其组织成数据 block 以便于阅读。

typedef struct _open
{
    int id;
    double length;
    double height;
    double origX;
    double origY;
    int frames;

    double thickness;
    double E;
    double v;
}CHBOpening;

typedef struct _panels
{
    int id;
    double length;
    double height;
    double origX;
    double origY;
    double origZ;
    double angle;
    int nOpenings;
    int nReinforcement;
    double *xReinf;
    double sx;
    double xReinf0;

    CHBUnit *chb;
    CHBOpening *openings[];
}CHBPanel;

typedef struct _chb
{
    int nStories;
    int nModes;
    int nIter;
    int nPanels;
    CHBPanel *panels[];
}CHBStructure;

int ReadPanelBlock (FILE *fp, CHBStructure *S)
{
    CHBOpening *openings = malloc(sizeof(CHBOpening));
    *S->panels = malloc(S->nPanels*sizeof(CHBPanel));
    for (i=0; i<S->nPanels; i++)
    {
        fscanf(fp,"%d",&S->panels[i]->id);
        fscanf(fp,"%lf",&S->panels[i]->length);
        fscanf(fp,"%lf",&S->panels[i]->height);
        fscanf(fp,"%lf",&S->panels[i]->angle);
        fscanf(fp,"%lf",&S->panels[i]->origX);
        fscanf(fp,"%lf",&S->panels[i]->origY);
        fscanf(fp,"%lf",&S->panels[i]->origZ);
        fscanf(fp,"%d",&S->panels[i]->nOpenings);
        if (S->panels[i]->nOpenings > 0)
        {
            for (j=0; j<S->panels[i]->nOpenings;j++)
            {
                openings = S->panels[i]->openings[j];
                fscanf(fp,"%d",&openings->id);
                fscanf(fp,"%lf",&openings->length);
                fscanf(fp,"%lf",&openings->height);
                fscanf(fp,"%lf",&openings->origX);
                fscanf(fp,"%lf",&openings->origY);
            }
        }
    }
    return 1;
}

编辑 1:我尝试通过在每一行中打印文本来跟踪错误发生的位置，它似乎在 ReadPanelBlock 函数的第一个 fscanf 函数中崩溃。

Answer 1

访问 S->panels[i]->openings[j] 是 UB ，因为您没有为该数组分配空间。

    if (S->panels[i].nOpenings > 0)
    {
         S->panels[i].openings = malloc(sizeof(CHBPanel)*S->panels[i].nOpenings);

         // inner for
    }

为 openings 指针预分配空间:

CHBOpening *openings = malloc(sizeof(CHBOpening));

将导致内存泄漏，因为地址将被 j 内部 for with code 丢失，因此没有代码会释放该内存

openings = S->panels[i]->openings[j];

你可以避免有一个指针而写

        for (j=0; j<S->panels[i].nOpenings;j++)
        {
            fscanf(fp,"%d",&S->panels[i].openings[j].id);
            fscanf(fp,"%lf",&S->panels[i].openings[j].length);
            fscanf(fp,"%lf",&S->panels[i].openings[j].height);
            fscanf(fp,"%lf",&S->panels[i].openings[j].origX);
            fscanf(fp,"%lf",&S->panels[i].openings[j].origY);
        }

在你的结构中 CHBPanel *panels[]; 和 CHBOpening *openings[]; 必须是:

CHBPanel *panels; 
CHBOpening *openings;

最后但并非最不重要的一件事:你必须研究一些关于指针和-> 和. 用法的东西。

你的代码应该是这样的:

int ReadPanelBlock (FILE *fp, CHBStructure *S)
{
    int i,j;
    S->panels = malloc(S->nPanels*sizeof(CHBPanel));
    for (i=0; i< S->nPanels; i++)
    {
        fscanf(fp,"%d",&S->panels[i].id);
        fscanf(fp,"%lf",&S->panels[i].length);
        fscanf(fp,"%lf",&S->panels[i].height);
        fscanf(fp,"%lf",&S->panels[i].angle);
        fscanf(fp,"%lf",&S->panels[i].origX);
        fscanf(fp,"%lf",&S->panels[i].origY);
        fscanf(fp,"%lf",&S->panels[i].origZ);
        fscanf(fp,"%d",&S->panels[i].nOpenings);
        if (S->panels[i].nOpenings > 0)
        {
            S->panels[i].openings = malloc(sizeof(CHBOpening)*S->panels[i].nOpenings);

            for (j=0; j<S->panels[i].nOpenings;j++)
            {
                fscanf(fp,"%d",&S->panels[i].openings[j].id);
                fscanf(fp,"%lf",&S->panels[i].openings[j].length);
                fscanf(fp,"%lf",&S->panels[i].openings[j].height);
                fscanf(fp,"%lf",&S->panels[i].openings[j].origX);
                fscanf(fp,"%lf",&S->panels[i].openings[j].origY);
            }
        }
    }
    return 1;
}