c++ - 指针 float 数组的第一次机会异常

Question

    int main(int argc, char** argv)
{
    printf("Enter the file name:\n");
    char inputFileLoc[100], outFileLoc[100];
    scanf("%s", inputFileLoc);
    int * n = 0;
    float rcoef[2];
    FILE * inFile = fopen("D:\\test.txt", "r");
    FILE * outFile = fopen(outFileLoc, "w");
    if (inFile == NULL)
    {
        printf("File not found at %s", inputFileLoc);
    }
    else
    {

        printf("How many data points should we read in?");
        scanf("%i", &n);
        float *xdata = (float *)calloc(sizeof(float), *n);
        float *ydata = (float *)calloc(sizeof(float), *n); 
        for (int i = 0; i < *n; i++)
        {
            fscanf(inFile, "%f%f", &xdata[i], &ydata[i]);
        }
        fregression(xdata, ydata, rcoef);
        printf("Where would you like to save the file to?\n");
        scanf("%s", outFileLoc);
        fprintf(outFile, "The slope and intercept are %f and %f", rcoef[0], rcoef[1]);
        free(xdata);
        free(ydata);
    }
    fclose(inFile);
    fclose(outFile);
    return 0;
}

我在“float *xdata = (float *).....”行收到错误，我不知道为什么？我是否缺少某种异常处理程序，因为这是我唯一能想到的事情的。

Answer 1

这是不正确的:

int * n = 0;

应改为

int n = 0;

scanf 应该获取要写入的地址，而不是指针的地址。即使您想使用指针，也应该分配内存并且 n 应该指向该指针。在这种情况下，您应该在传递给 scanf 时将 & 删除为 n，即 scanf("%i", n); 应该没问题。