经过大量工作后，我已使拼写器正常工作，并且可以正确编译并运行，但是当我通过valgrind运行它时，会发生大量内存泄漏。我检查了我的代码，但没有发现任何错误。是什么原因导致内存泄漏？免费不能按预期工作吗？
// Implements a dictionary's functionality
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <strings.h>
#include "dictionary.h"
// Represents a node in a hash table
typedef struct node
{
char word[LENGTH + 1];
struct node *next;
}
node;
// Number of buckets in hash table
const unsigned int N = 26;
// Hash table
node *table[N];
//Count words when written in hashtable
int wordcount = 0;
// Returns true if word is in dictionary else false
bool check(const char *word)
{
//Hashes word for comparing
int cmp = hash(word);
//Access linked list based on hashtable index
node* point = table[cmp];
//Check if word is on linked list
while (point != NULL)
{
if (strcasecmp(point->word, word) == 0)
{
return true;
}
point = point->next;
}
return false;
}
// Hashes word to a number
unsigned int hash(const char *word)
{
//Hashfunction source: https://study.cs50.net/hashtables
//Hash on first letter of string
int hash = toupper(word[0]) - 'A';
return hash % N;
}
// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)
{
//Opens file in read mode
FILE *file =fopen(dictionary,"r");
//Checks if there actually is a file
if (file == NULL)
{
return false;
}
char word[LENGTH + 1];
//Iterate through file while checking if end of file has not been reached
while(fscanf(file, "%s",word) != EOF)
{
//Creates new node
node* n = malloc(sizeof(node));
//Checks if node is NULL
if (n == NULL)
{
return false;
}
//Copy word from dictionary to hashtable
strcpy(n->word, word);
//Hashes word to determine index
int h = hash(n->word);
//Inserts word on linked list
n->next = table[h];
table[h] = n;
wordcount++;
}
return true;
}
// Returns number of words in dictionary if loaded else 0 if not yet loaded
unsigned int size(void)
{
return wordcount;
}
// Unloads dictionary from memory, returning true if successful else false
bool unload(void)
{
//Indicates which linked list is currently being freed
int list = 0;
for (int i = 0; i < N;i++)
{
//Access linked list based on cmp
node* cursor = table[list];
node* tmp = cursor;
while (cursor != NULL)
{
cursor = cursor->next;
free(tmp);
node* tpm = cursor;
}
list++;
}
return true;
}
Valgrind错误消息
~/pset5/speller/ $ valgrind ./speller texts/cat.txt
==1749== Memcheck, a memory error detector
==1749== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==1749== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==1749== Command: ./speller texts/cat.txt
==1749==
MISSPELLED WORDS
==1749== Invalid free() / delete / delete[] / realloc()
==1749== at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x40126A: unload (dictionary.c:106)
==1749== by 0x400E09: main (speller.c:152)
==1749== Address 0x56e9670 is 0 bytes inside a block of size 56 free'd
==1749== at 0x4C30D3B: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x40126A: unload (dictionary.c:106)
==1749== by 0x400E09: main (speller.c:152)
==1749== Block was alloc'd at
==1749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x401172: load (dictionary.c:69)
==1749== by 0x400964: main (speller.c:40)
==1749==
WORDS MISSPELLED: 0
WORDS IN DICTIONARY: 143091
WORDS IN TEXT: 6
TIME IN load: 1.23
TIME IN check: 0.04
TIME IN size: 0.00
TIME IN unload: 0.11
TIME IN TOTAL: 1.38
==1749==
==1749== HEAP SUMMARY:
==1749== in use at exit: 8,012,192 bytes in 143,066 blocks
==1749== total heap usage: 143,096 allocs, 143,095 frees, 8,023,416 bytes allocated
==1749==
==1749== 552 bytes in 1 blocks are still reachable in loss record 1 of 3
==1749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x5258E49: __fopen_internal (iofopen.c:65)
==1749== by 0x5258E49: fopen@@GLIBC_2.2.5 (iofopen.c:89)
==1749== by 0x40112E: load (dictionary.c:58)
==1749== by 0x400964: main (speller.c:40)
==1749==
==1749== 8,010,184 bytes in 143,039 blocks are indirectly lost in loss record 2 of 3
==1749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x401172: load (dictionary.c:69)
==1749== by 0x400964: main (speller.c:40)
==1749==
==1749== 8,011,640 (1,456 direct, 8,010,184 indirect) bytes in 26 blocks are definitely lost in loss record 3 of 3
==1749== at 0x4C2FB0F: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==1749== by 0x401172: load (dictionary.c:69)
==1749== by 0x400964: main (speller.c:40)
==1749==
==1749== LEAK SUMMARY:
==1749== definitely lost: 1,456 bytes in 26 blocks
==1749== indirectly lost: 8,010,184 bytes in 143,039 blocks
==1749== possibly lost: 0 bytes in 0 blocks
==1749== still reachable: 552 bytes in 1 blocks
==1749== suppressed: 0 bytes in 0 blocks
==1749==
==1749== For counts of detected and suppressed errors, rerun with: -v
==1749== ERROR SUMMARY: 143066 errors from 2 contexts (suppressed: 0 fr
om 0)
答案 0 :(得分：0)
首先，您的加载功能错误。让我们一步一步地从while循环开始：
node* n并对其进行分配n是否不为空n h来存储单词的哈希值n->next = table[h]，其中table[h]当前等于NULL 解决方法（为方便起见，某些变量名称已更改）：
// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary){
//Data holds a single dictionary word
char data[LENGTH + 1];
//Open dictionary file
FILE* list = fopen(dictionary, "r");
if(list == NULL){
printf("File is missing.\n");
return 1;
}
while(fscanf(list, "%s", data) != EOF){
//Store word in a node
node *new_word = malloc(sizeof(node));
if(new_word == NULL){
return 1;
}
strcpy(new_word->word, data);
new_word -> next = NULL; //We want to initially set it to null incase this is the first word in table[hash_index]
//hash word to obtain hash value
int hash_index = hash(data);
//insert node into hashtable at that location
if(table[hash_index] == NULL){
table[hash_index] = new_word;
}
else{
new_word -> next = table[hash_index];
table[hash_index] = new_word;
}
num_words++;
}
fclose(list); //Make sure to add this as this will erase the `reachable` error in valgrind
return true;
}
这只是生活质量的改善，但是您将unload()更改为此：
for(int i = 0; i < N; i++){
while(table[i] != NULL){
node *tmp = table[i] -> next;
free(table[i]);
table[i] = tmp;
}
}