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)
答案 0 :(得分：0)
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。