Question

在我正在处理的哈希字典中，根据GDB，数组已经从500调整为1000.它崩溃尝试添加的数组索引是799，所以它不会超出范围......我不是确定为什么它会出现断裂，特别是在看似无害的线路上。这是相关的代码。

int main(int argc, char **argv)
{
FILE *src = fopen(argv[1], "r");
int algnum = 1;
char input[40];
struct HT *table = create();


if (argc == 3)
{
    if (strcmp(argv[2], "0") == 0)
    {
        algnum = 0; 
    }
    else if (strcmp(argv[2], "1") == 0)
    {
        algnum = 1;
    }
}

while(fgets(input, 40, src) != 0)
{
    int i = 0;
    while(input[i] != '\0')
    {
        i++;
    }

    struct word *wrd = malloc(sizeof(struct word));
    wrd->letters = input;
    wrd->length = i;
    if (algnum = 0)
    {
        add(table, wrd, &alg0);
    }
    else if (algnum = 1)
    {
        add(table, wrd, &alg1);
    }
}
}

然后在包含文件中......

struct HT* create() 
{
struct HT* table = malloc(sizeof(struct HT));
table->entries = 0;
table->num_buckets = 500;
table->largest_bucket = 0;
table->occupied_buckets = 0;
table->buckets = malloc(500 * sizeof(struct bucket*));
int i;  
for (i = 0; i<500; i++)
{
    table->buckets[i] = malloc(sizeof(struct bucket));
    table->buckets[i]->num_items = 0;
}
return table;   
}

struct HT* resize(struct HT* table, int(*alg)(struct word *wrd)) 
{
struct HT* table_new = malloc(sizeof(struct HT));
int new_size = 2*table->num_buckets;
table_new->buckets = malloc(new_size*sizeof(struct bucket*));
int i;  
for (i = 0; i < new_size; i++)
{
    table->buckets[i] = malloc(sizeof(struct bucket));
    table->buckets[i]->num_items = 0;
}
table_new->num_buckets = new_size;
table_new->occupied_buckets = 0;
table_new->entries = 0;
table_new->largest_bucket = 0;

struct word* wrd_temp = malloc(sizeof(struct word));
struct item* item_temp = malloc(sizeof(struct item));
for (i = 0; i<table->num_buckets; i++)
{
    item_temp = table->buckets[i]->head;
    while(item_temp != 0)
    {
        wrd_temp = item_temp->wrd;
        add(table_new, wrd_temp, alg);
        item_temp = item_temp->next;
    }
}
quit(table);
return table_new;
}

void add(struct HT* table, struct word *wrd, int(*alg)(struct word *wrd)) 
{
if ((double)table->entries / (double)table->num_buckets > .75)
{
    table = resize(table, alg);
}   
sort(wrd);
int code = alg(wrd);
code = code % table->num_buckets;
struct item* item_temp = malloc(sizeof(struct item));
struct item* item_add = malloc(sizeof(struct item));
item_add->wrd = wrd;
if (table->buckets[code]->head == 0)
{
    table->buckets[code]->head = item_add;
    table->occupied_buckets++;
}
else
{
    item_temp = table->buckets[code]->head;
    while (item_temp->next != 0) {
        item_temp = item_temp->next;
    }
    item_temp->next = item_add;
}
table->buckets[code]->num_items++;
table->entries++;
if (table->buckets[code]->num_items > table->largest_bucket)
{
    table->largest_bucket = table->buckets[code]->num_items;
}
}

编辑：它崩溃的线是：

编程接收信号SIGSEGV，分段故障。添加0x0000000000400cbd（表= 0x613cc0，wrd = 0x613ca0，alg = 0x400942）at ht.c：118 118 if（table-＆gt; buckets [code] - ＆gt; head == 0）

请求信息：

（gdb）print table-＆gt; buckets [799] $ 2 =（struct bucket *）0x0

Answer 1

问题是在resize中您创建了一个全新的HT结构。但是在add中，您不会将此回传给调用链，因此在main中您仍然拥有旧的 HT结构。

作为一个额外的注释，你永远不会free任何东西，所以你有很多内存泄漏。

在main中，您可以创建一个新表格。让我们调用此表1.稍后，当它正在变满时，您将创建一个 new 表，让我们调用它2.这个新表由resize返回并在add中使用。但是当add返回时，main函数仍然有一个指向表1的指针。

因此，下次调用add时，main函数会传递表1，表1太小，因此调用resize并创建另一个表，3，仅在add本地使用。依旧等等......

至少375次成功参赛后的代码段错误

1 个答案: