我的代码有问题。我得到一个分段错误错误，我理解这是一个悬空指针问题（通常）或错误的内存分配。编译器没有显示问题可能出现在哪一行，所以我的问题是如何进一步关注这些问题？我的问题在代码中会在哪里？ 这是我的代码：
`#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define ARRAY_SIZE(a) sizeof(a)/sizeof(a[0])
#define ALPHABET_SIZE (256)
#define CHAR_TO_INDEX(c) ((int)c - (int)'a')
#define LEVELS 255
// trie node
struct n
{
char value,level,isLeaf;
struct n* children[ALPHABET_SIZE];
struct n* failLink;
};
typedef struct n node;
//trie
struct t
{
node *root;
int count;
};
typedef struct t trie;
void bytesCpy(char *to, char *from, int len)
{
int i;
for(i=0;i<len;i++)
{
to[i]=from[i];
}
}
// Returns new trie node (initialized to NULLs)
node *getNode(trie *t, char value,char level)
{
node *pNode = NULL;
pNode = (node *)malloc(sizeof(node));
if (pNode)
{
printf("ok\n");
int i;
for (i = 0; i < ALPHABET_SIZE; i++)
{
pNode->children[i] = NULL;
}
pNode->failLink = t->root;
pNode->value=value;
pNode->level=level;
pNode->isLeaf=0;
}
else
printf("error\n");
return pNode;
}
// Initializes trie (root is dummy node)
void initialize(trie *t)
{
t->root = getNode(t, '[', 0);
//t->count = 0;
}
// If not present, inserts key into trie
// If the key is prefix of trie node, just marks leaf node
void insert(trie *t, char key[], int len)
{
int level;
char value;
node *node = t->root;
for (level = 0; level<len; level++)
{
value = key[level];
printf("value: %c\n",value);
if (node->children[value] == NULL)
{
node->children[value] = getNode(t, value, level+1);
}
node = node->children[value];
}
node->isLeaf=1;
}
// Returns non zero, if key presents in trie
int search(trie *t, char key[])
{
int level;
int length = strlen(key);
int value;
node *node;
node = t->root;
for (level = 0; level < length; level++)
{
value = key[level];//CHAR_TO_INDEX(key[level]);
if (!node->children[value])
{
node = node->failLink;
return 0;
}
node = node->children[value];
}
return (0 != node);// && node->value);
}
void search1(trie *t, char *c, int len)
{
node *curNode = t->root;
int i;
for(i=0; i<=len; i++)
{
printf("i=%d curnode=%p\n",i,curNode);
if(curNode->isLeaf) //leaf: cuvant gasit
{
printf("if1 curGasit \n");
do{
curNode=curNode->failLink;
if(curNode->isLeaf)
printf("if1 curGasit \n");
else break;
}while(1);
continue;
}
else //nu e gasit inca
{
if(curNode->children[c[i]]==NULL) //fail
{
printf("if2\n");
curNode = curNode->failLink;
continue;
}
else //litera gasita: go on
{
printf("el2\n");
curNode=curNode->children[c[i]];
}
}
}
printf("end of search\n");
}
node* searchAux(trie *t, node *curRoot, char cuv[], char len, int level ,int failLevel)
{
char cuvAux[1024];
bytesCpy(cuvAux,cuv,len);
printf("searchAux level:%d cuvAux:%s curRootLevel:%d\n",level,cuvAux,curRoot->level);
if(cuvAux[level+1] == '\0') //got to the end of cuvAux
{
printf("1st if\n");
return curRoot;
}
if(curRoot->children[cuvAux[level+1]] == NULL) //fail: letter not found
{
printf("3rd if\n");
return searchAux(t, t->root, &cuvAux[failLevel+1], len, 0, failLevel+1);
}
else //letter found: go on
{
printf("3rd else\n");
if(cuvAux[level+2] == '\0') //the found letter was the last of the string
{
printf("4th if\n");
return curRoot->children[cuvAux[level+1]]; //return final pointer
}
else //the found letter was not the last of the string: continue with the next one
{
printf("4th else\n");
return searchAux(t, curRoot->children[cuvAux[level+1]], cuvAux, len, level+1, failLevel);
}
}
}
void createFailLinks(trie *t, node* curRoot, char cuv[], int level)
{
int i;
char cuvAux[1024];
bytesCpy(cuvAux,cuv,1024);
if(curRoot == NULL)
return;
for(i=0;i<ALPHABET_SIZE/*curRoot->children[i] != NULL*/;i++)
{
if(curRoot->children[i] == NULL)
continue;
else
{
cuvAux[level] = curRoot->children[i]->value;
printf("createFailLinks %c%d\n",cuvAux[level],curRoot->children[i]->level);
curRoot->children[i]->failLink = searchAux(t, t->root, cuvAux, level+1, 0, 0);
createFailLinks(t,curRoot->children[i],cuvAux,level+1);
}
}
printf("got\n");
}
void printTrie(node *curRoot)
{
int i;
if(curRoot == NULL)
return;
printf("%c: ", curRoot->value);
for(i=0;i<ALPHABET_SIZE;i++)
if(curRoot->children[i] != NULL)
{
printf("%c ", i);
}
printf("\n");
for(i=0;i<ALPHABET_SIZE;i++)
if(curRoot->children[i] != NULL)
{
printTrie(curRoot->children[i]);
}
}
void checkLinks(node* curRoot)
{
int i;
if(curRoot == NULL)
return;
printf("node %c%d: ",curRoot->value,curRoot->level);
for(i=0;i<256;i++)
if(curRoot->children[i] != NULL)
printf("\n\t%c%d:%c%d",curRoot->children[i]->value, curRoot->children[i]->level, curRoot->children[i]->failLink->value,curRoot->children[i]->failLink->level);
printf("\n");
for(i=0;i<256;i++)
if(curRoot->children[i] != NULL)
checkLinks(curRoot->children[i]);
}
int mai()
{
FILE *fd = fopen("VirusDatabase.txt","r");//O_RDONLY);
int i;
char c;
for(i=0;i<1000;i++)
{
fscanf(fd, "%c", &c);
printf("%c",c);
}
}
int main()
{
// Input keys (use only 'a' through 'z' and lower case)
char keys[][1024] = { "he", "she", "her", "his", "heres"};
char cuv[] = {'\0','\0','\0','\0','\0','\0'};
trie t;
char output[][32] = { "Not present in trie", "Present in trie" };
int i;
char text[]={"andreiherutshevlastashecristihiskatjaheres"};
initialize(&t);
// Construct trie
for (i = 0; i < ARRAY_SIZE(keys); i++)
{
insert(&t, keys[i], strlen(keys[i]));
}
createFailLinks(&t, t.root, cuv, 0);
printTrie(t.root);
printf("\n\n");
checkLinks(t.root);
search1(&t, text, strlen(text));
return 0;
// Search for different keys
printf("%s --- %s\n", "abcd", output[search(&t, "abcd")]);
printf("%s --- %s\n", "ab", output[search(&t, "ab")]);
printf("%s --- %s\n", "ccdd", output[search(&t, "ccdd")]);
printf("%s --- %s\n", "thaw", output[search(&t, "thaw")]);
return 0;
char a = getchar();
}`
答案 0 :(得分：2)
您是否可以访问调试器？我在调试器中运行您的代码并在第157行获取内存访问冲突：
return searchAux(t, t->root, &cuvAux[failLevel+1], len, 0, failLevel+1);
你似乎在递归地调用searchAux。即你有：
node* searchAux(trie *t, node *curRoot, char cuv[], char len, int level ,int failLevel)
{
char cuvAux[1024];
...
return searchAux(t, t->root, &cuvAux[failLevel+1], len, 0, failLevel+1);
...
无论如何，最终缓冲区大小变量failLevel超过了缓冲区的大小，因此您尝试访问数组边界之外的内存，这就是您获得访问冲突的原因。
最简单的调试方法是使用交互式调试器。在Windows上有一个免费版本的Visual Studio，它有一个非常好的调试器。在linux上你可以使用GDB。
如果没有，你可以嵌入print语句在崩溃前打印出变量。
答案 1 :(得分：0)
您可以在代码行添加print语句。
#include <iostream>
std::cout << "At Line: " << __LINE__ << endl;
将它放在各种代码行中，你可以看到哪些行被执行，并找到它崩溃的地方。
这适用于C ++。我的错。同样的想法，但是放入printf（）语句并查看它停止执行的位置以缩小崩溃位置。