當我嘗試釋放我的結構時，程式由于段錯誤而崩潰。檢查程式valgrind我發現：
==9761== Invalid free() / delete / delete[] / realloc()
==9761== at 0x484827F: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==9761== by 0x109242: destroyHashTable (hashtable.c:38)
==9761== by 0x10942E: main (hashtable_main.c:17)
==9761== Address 0x1ffefffa70 is on thread 1's stack
==9761== in frame #2, created by main (hashtable_main.c:7)
我真的不能說比不知道如何解決它更有用的東西。崩潰發生在infree(ht)期間。我究竟做錯了什么？destroyHashTable(ht)hashtable.c
代碼下方hashTable_main.c：
#include <stdio.h>
#include <stdlib.h>
#include "hashtable.h"
int main() {
hashTable* ht = NULL;
initHashTable(&ht);
int totalColCount = 0;
totalColCount = addHashTableEntry(&ht, "PRPR2");
destroyHashTable(&ht);
return EXIT_SUCCESS;
}
hashtable.c：
#include <stdlib.h>
#include <stdio.h>
#include "hashtable.h"
/* private internal API */
int hash_funktion(char *string);
hashtableEntry* createTableEntry(char* newKey) ;
/* end of private internal API */
int hash_funktion(char *string) {
unsigned int hash_adresse;
unsigned char *pointer;
hash_adresse = 0;
pointer = (unsigned char *) string;
while(*pointer != '\0') {
hash_adresse = 19 * hash_adresse *pointer;
pointer ;
}
return hash_adresse % MAX_HASH;
}
hashtableEntry* createTableEntry(char* newKey) {
hashtableEntry* e = (hashtableEntry*) malloc (sizeof(hashtableEntry));
e->hashKey = newKey;
return e;
}
void initHashTable(hashTable* ht) {
ht = (hashTable*) malloc (sizeof (struct hashTable));
ht->table = (hashtableEntry*) malloc (MAX_HASH * sizeof (hashtableEntry));
}
void destroyHashTable(hashTable* ht) {
if (ht) {
free(ht);
ht = NULL;
}
}
int addHashTableEntry(hashtableEntry* ht, char* keyValue) {
hashtableEntry *e = createTableEntry(keyValue);
int colCounter = 0;
int hashValue = hash_funktion(keyValue);
if (ht[hashValue].hashKey == NULL) {
ht[hashValue] = *e;
return 0;
} else {
int newVal = (hashValue 1) % MAX_HASH;
colCounter ;
while (ht[newVal].hashKey != NULL && newVal != hashValue ) {
newVal = (newVal 1) % MAX_HASH;
colCounter ;
}
if (newVal != hashValue) {
ht[newVal] = *e;
return colCounter;
} else {
return -1;
}
}
}
bool searchValue(hashtableEntry* ht, char* searchValue) {
for (int i = 0; i < MAX_HASH; i )
{
if(ht[i].hashKey == searchValue) {
return true;
}
}
return false;
}
和hashtable.h：
#pragma once
#define MAX_HASH 20
#include <stdbool.h>
typedef struct hashtableEntry {
char* hashKey;
} hashtableEntry;
typedef struct hashTable {
hashtableEntry* table;
int elemCount;
} hashTable;
void initHashTable(hashTable* ht);
void destroyHashTable(hashTable* ht);
int addHashTableEntry(hashtableEntry* ht, char* keyValue);
bool searchValue(hashtableEntry* ht, char* searchValue);
uj5u.com熱心網友回復：
一開始就沒有哈希表。問題在于initHashTable。它應該接受一個雙指標，因為它被賦予了一個指向它應該初始化的指標的指標。盡管簽入，它仍可能出現段錯誤的原因destroyHashTable是指標未初始化，并且在程式執行開始時可能為非零。
void initHashTable(hashTable** ht) {
*ht = (hashTable*) malloc (sizeof (struct hashTable));
(*ht)->table = (hashtableEntry*) malloc (MAX_HASH * sizeof (hashtableEntry));
}
您可能會發現回傳新創建的哈希表更容易。這更好地表達了initHashTable給你一個新的hashTable *價值。
hashTable *initHashTable() {
hashTable *ht = (hashTable *) malloc (sizeof (struct hashTable));
ht.table = (hashtableEntry *) malloc (MAX_HASH * sizeof (hashtableEntry));
return ht;
}
還有很多其他地方沒有正確處理指標。
void doThing(Foo *foo) {
// This changes foo, but not the data foo points to.
foo = something;
// This changes the data foo points to
*foo = someOtherThing;
}
void doStuff() {
Foo *foo;
// This is incorrect since it creates a double pointer. doThing would need to
// be defined as "void doThing(Foo **foo)" to be correct.
doThing(&foo);
// Instead we can just pass the existing pointer
doThing(foo);
// We only need to create a reference if the value does not start out as a pointer
Foo bar;
doThing(&bar);
}
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