Question

我正在尝试为给定的一组0.1百万个唯一密钥实现完美的哈希函数。在开发代码的过程中，我得到了分段错误。问题可能出在insert_hash函数中。但是作为C语言的初学者，iam无法弄清楚。这是完整的代码。

# include<stdio.h>
# include <stdlib.h>
# define array_size 1000000
/* Function to calculate x raised to the power y */
int keys[1000000];
unsigned long long p = 100000000019;
int power(int x, unsigned int y) {
if (y == 0)
    return 1;
else if (y % 2 == 0)
    return power(x, y / 2) * power(x, y / 2);
else
    return x * power(x, y / 2) * power(x, y / 2);
 }
 int rand_number() {
 //generate 9 digit random numbers with in range a and b;
 int a = 100000000, b = 999999999, num;
 num = rand() % (b - a + 1) + a;
 return num;
  }

 struct hash {
 int count, a, b, m;
 int *dyn_array;
 }*ptr[array_size], *tmp = NULL;
 void insert_hashkey(int hash1, int key) {
 int arraysize = 1, i, hash_value;
 static int primaryhashcount = 0, secondhashcount = 0;

    if (ptr[hash1]->count == 1) {
    primaryhashcount++;
    //ptr[hash1]=NULL;
    ptr[hash1]->dyn_array = (int*) malloc((sizeof(int)) * arraysize);
    if (ptr[hash1]->dyn_array == NULL) {
        printf("out of memory\n");
        exit(1);
    }
    ptr[hash1]->dyn_array[0] = key;
    printf("\n ptr[%d]->dyn_array[0]=%d  %d", hash1, key, primaryhashcount);
    } else {
    printf("\n entered in to else part");
    //ptr[hash1]=a;
    secondhashcount++;

    tmp = (struct hash*) malloc(sizeof(struct hash));
    tmp->m = (ptr[hash1]->count) * (ptr[hash1]->count);
    tmp->count = (ptr[hash1]->count);
    --(ptr[hash1]->count);
    arraysize = (ptr[hash1]->count) * (ptr[hash1]->count);
    //tmp=a;
    tmp->dyn_array = (int*) malloc((sizeof(int)) * arraysize);
    if (tmp->dyn_array == NULL) {
        printf("out of memory\n");
        exit(1);
    }
    tmp->a = rand_number();
    tmp->b = rand_number();
    for (i = 0; i < tmp->m; i++)
        tmp->dyn_array[i] = -1;
    for (i = 0; i < arraysize; i++) {
        if (ptr[hash1]->dyn_array[i] != -1) {
            hash_value = (((tmp->a) * (ptr[hash1]->dyn_array[i]) + tmp->b)
                    % p) % (tmp->m);
            printf("\n first if success");
            if (tmp->dyn_array[hash_value] == -1) {
                tmp->dyn_array[hash_value] = ptr[hash1]->dyn_array[i];
                        secondhashcount, tmp->count, hash1, hash_value,
                        (ptr[hash1]->dyn_array[i]), tmp->m);
             }
         }

     }
    hash_value = (((tmp->a) * key + tmp->b) % p) % (tmp->m);
     if (tmp->dyn_array[hash_value] == -1) {
         tmp->dyn_array[hash_value] = key;
         printf(
                 "\n second hash count=%d count=%d ptr[%d]->dyn_array[%d]=%d,m=%d",
                 secondhashcount, tmp->count, hash1, hash_value, key,
                 tmp->m);
     } else
        printf("\n collision");
     free(ptr[hash1]->dyn_array);
     free(ptr[hash1]);
    ptr[hash1] = tmp;
    tmp = NULL;

   }
  }

 int hash_fun(int key, int a, int b, unsigned long long p) {
 int hash_val;
 hash_val = (((a * key) + b) % p) % 1000000;
 return hash_val;
  }
 void main() {
int i = 0, hash1, count = 0, j;
 char ch;
 int a, b, m;
time_t t;
FILE *fp;
fp = fopen("input.in", "r");
/* Intializes rand_num number generator */
srand((unsigned) time(&t));

for (i = 0; i < array_size; i++) {

    ptr[i] = NULL;
}
a = 774877719;
b = 271009528;
i = 0;
while (fscanf(fp, "%d", &keys[i++]) == 1)
    ;
printf("\n read keys successfully from file");
//finding the hash values of array
for (i = 0; i < 100000; i++) {
    hash1 = hash_fun(keys[i], a, b, p);
    if (ptr[hash1] == NULL) {
        // create a structure of ni2 elements for each pointer where ni is the            number of collisions
        // printf("\nmaximum size=%d",malloc(MAX));

        ptr[hash1] = (struct hash *) malloc(sizeof(struct hash));
        if (ptr[hash1] == NULL) {
            printf("out of memory\n");
            exit(1);
        }
        ptr[hash1]->count = 1;
        insert_hashkey(hash1, keys[i]);

    } else {
        ++(ptr[hash1]->count);
        insert_hashkey(hash1, keys[i]);
    }
}
 for (i = 0; i < array_size; i++) {
    if (ptr[hash1] != NULL)
        free(ptr[hash1]);
}
}

2.以下是valgrind的报告。但我无法在我的代码中找到确切的问题，因为在尝试修复6小时后，一切对我来说都是正确的。请在此背景下帮助我

  ==3595== LEAK SUMMARY:
  ==3595==    definitely lost: 4 bytes in 1 blocks
  ==3595==    indirectly lost: 0 bytes in 0 blocks
  ==3595==      possibly lost: 0 bytes in 0 blocks
  ==3595==    still reachable: 2,287,100 bytes in 190,411 blocks
==3595==         suppressed: 0 bytes in 0 blocks
==3595== Reachable blocks (those to which a pointer was found) are not shown.
==3595== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==3595== 
==3595== ERROR SUMMARY: 1026216 errors from 11 contexts (suppressed: 0 from 0)
==3595== 
==3595== 62 errors in context 1 of 11:
==3595== Invalid write of size 4
==3595==    at 0x8048A46: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x449be94 is 4 bytes after a block of size 16 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 110 errors in context 2 of 11:
==3595== Invalid read of size 4
==3595==    at 0x8048976: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x439a804 is 0 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 110 errors in context 3 of 11:
==3595== Invalid read of size 4
==3595==    at 0x8048955: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x439a804 is 0 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 113 errors in context 4 of 11:
==3595== Invalid read of size 4
==3595==    at 0x80488C4: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x439a804 is 0 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 457 errors in context 5 of 11:
==3595== Invalid read of size 4
==3595==    at 0x804889C: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x4487004 is 0 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 3552 errors in context 6 of 11:
==3595== Invalid read of size 4
==3595==    at 0x8048A2C: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x425110c is 8 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 3561 errors in context 7 of 11:
==3595== Invalid write of size 4
==3595==    at 0x8048957: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x425110c is 8 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 3561 errors in context 8 of 11:
==3595== Invalid read of size 4
==3595==    at 0x8048929: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x425110c is 8 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 14690 errors in context 9 of 11:
==3595== Invalid write of size 4
==3595==    at 0x8048864: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x4228b84 is 0 bytes after a block of size 4 alloc'd
==3595==    at 0x402A17C: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048807: insert_hashkey (in /home/abhimint/Desktop/hashing/a.out)
==3595==    by 0x8048CEA: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== 
==3595== 999999 errors in context 10 of 11:
==3595== Invalid free() / delete / delete[] / realloc()
==3595==    at 0x402B3D8: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048D29: main (in /home/abhimint/Desktop/hashing/a.out)
==3595==  Address 0x4e3b6b0 is 0 bytes inside a block of size 20 free'd
==3595==    at 0x402B3D8: free (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
==3595==    by 0x8048D29: main (in /home/abhimint/Desktop/hashing/a.out)
==3595== 
==3595== ERROR SUMMARY: 1026216 errors from 11 contexts (suppressed: 0 from 0)

Answer 1

尝试在valgrind中使用：--trace-origins=yes 对于每个无效的读/写，它将为您提供函数名称。

无效阅读意味着您可能正在尝试阅读尚未初始化或已被删除的变量。

valgrind-invalid读写操作

1 个答案: