Question

我在一段相当简单的代码上遇到了一个奇怪的问题。代码的相关部分如下：

void foo(int32 in_sd_id, int32 out_sd_id)
{
    int32 nsds;                     /* number of data sets in the file */
    int32 nattr;                    /* number of global attributes in the file */
    int32 attr_cnt;                 /* count of number of attribute */
    int32 attr_index;               /* attribute index */
    int32 attr_type, attr_size;     /* attribute type and size */
    char attr_name[40];  



    ret = SDfileinfo(in_sd_id, &nsds, &nattr);
    printf("nattr is %d\n", nattr);
    /* test to see if num_datasets and num_global_attr can be retrieved from in_sd_id */
    if (ret == -1)
        {
        fprintf(stdout, "cannot read information from input file \n");
        exit(EXIT_FAILURE);
        }
    else
        {
        /* loop through each global attributes */
        for (attr_index=0; attr_index<nattr; attr_index++)
        {
            printf("attr_index:nattr is %d:%d\n", attr_index, nattr);
            /* test to see if the file or dataset do indeed contain attributes */
            if (SDattrinfo(in_sd_id, attr_index, attr_name, &attr_type, &attr_cnt) == FAIL)
            fprintf(stdout, "Cannot read information for attribute %d\n", attr_index);
            else
            {
                DO SOMETHING 
            }
        }
    }
}

问题在于nattr变量。比如说nattr 11，for，nattr循环，当我打印11的值时，我会将其作为1869501279获取一段时间然后突然它会爆炸到像nattr这样的数字。我没有在其余代码中使用此nattr is 11 attr_index:nattr is 0:11 attr_index:nattr is 1:11 attr_index:nattr is 2:11 attr_index:nattr is 3:11 attr_index:nattr is 4:11 attr_index:nattr is 5:11 attr_index:nattr is 6:11 attr_index:nattr is 7:11 attr_index:nattr is 8:1869501279 attr_index:nattr is 9:1850957672 attr_index:nattr is 10:1850957672 attr_index:nattr is 11:1850957672 Cannot read information for attribute 11 attr_index:nattr is 12:1850957672 Cannot read information for attribute 12 attr_index:nattr is 13:1850957672变量执行任何其他操作。我有双重和牛肚检查。所以我不确定它为什么突然爆炸。下面给出了一个样本运行的调试语句：

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有关此处可能发生的事情的任何帮助。感谢

Answer 1

你（非常）可能有缓冲区溢出。我敢打赌，您正试图向attr_name写入大于39的索引。

但不要只增加attr_name的大小。您需要了解// DO SOMETHING代码中的内容。

C变量突然爆发

1 个答案: