【发布时间】：2019-05-31 17:02:37
【问题描述】：
运行代码时出现错误：ds(57203,0x70000fba3000) malloc: * 对象 0x7ff875402848 错误：已释放对象的校验和不正确 - 对象在被释放后可能已被修改。 * 在 malloc_error_break 中设置断点进行调试
有时它可以工作，有时它在尝试 malloc 新节点后崩溃（请参阅 createNode 函数），所以我怀疑错误来自那里。
我做错了什么？我该如何解决？
我已尝试调试代码并更改了几个 malloc，但无法解决问题。
正如我之前所说，我怀疑错误出在 createNode 函数中。
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>
void* threadFunction(void* searchTerm);
void scanDirName(char * path, char * searchTerm);
char* rootSD;
pthread_mutex_t qlock;
struct Node {
char* data;
struct Node* next;
};
// Two glboal variables to store address of front and rear nodes.
struct Node* front = NULL;
struct Node* rear = NULL;
// To Enqueue an integer
void Enqueue(char* x) {
pthread_mutex_lock(&qlock);
/* printf("\nhere\n");*/
struct Node* temp = (struct Node*)malloc(sizeof(struct Node));
temp->data =x;
temp->next = NULL;
if(front == NULL && rear == NULL){
front = rear = temp;
pthread_mutex_unlock(&qlock);
return;
}
rear->next = temp;
rear = temp;
pthread_mutex_unlock(&qlock);
}
// To Dequeue an integer.
char* Dequeue() {
pthread_mutex_lock(&qlock);
struct Node* temp = front;
if(front == NULL) {
pthread_mutex_unlock(&qlock);
return NULL;
}
char* data;
data = front->data;
if(front == rear) {
front = rear = NULL;
}
else {
front = front->next;
}
free(temp);
pthread_mutex_unlock(&qlock);
return data;
}
void Print() {
struct Node* temp = front;
while(temp != NULL) {
printf("%s ",temp->data);
temp = temp->next;
}
printf("\n");
}
void* threadFunction(void* st){
char* filepath;
filepath = NULL;
char* searchTerm;
searchTerm = (char*)st;
while (filepath == NULL) {
filepath = Dequeue();
}
printf("about to enter with %s, %s\n",filepath, searchTerm);
fflush(stdout);
scanDirName(filepath, searchTerm);
if (strcmp(filepath,rootSD) != 0)
free(filepath);
return (void*)1;
}
void scanDirName(char * path, char * searchTerm){
DIR * d = opendir(path); // open the path
char* str3;
if(d==NULL) return; // if was not able return
;
struct dirent * dir; // for the directory entries
while ((dir = readdir(d)) != NULL) // if we were able to read somehting from the directory
{
if(dir-> d_type == DT_DIR){ //
if (dir->d_type == DT_DIR && strcmp(dir->d_name, ".") != 0 & strcmp(dir->d_name, "..") != 0) // if it is a directory
{
str3 = malloc(1+strlen("/") + strlen(searchTerm)+ strlen(dir->d_name) );
if (!str3){
return;
}
strcpy(str3, path);
strcat(str3, "/");
strcat(str3, dir->d_name);
printf("\n---\n%s\n---\n",str3);
Enqueue(str3);
printf("Succ");
}
} else if(dir-> d_type == DT_REG){ //
if(strstr(dir->d_name, searchTerm)){
printf("%s/%s\n", path, dir->d_name);
}
}
}
closedir(d); // finally close the directory
}
int main(int argc, char* argv[]){
if (argc != 4){
printf("ERROR\n");
exit(1);
}
char* rootSearchDir = argv[1];
char* searchTerm = argv[2];
int threadsNumber = atoi(argv[3]);
pthread_t threadsCollection[threadsNumber];
rootSD = rootSearchDir;
Enqueue(rootSearchDir);
int i;
for (i=0; i<threadsNumber; i++){
if(pthread_create(&threadsCollection[i], NULL, threadFunction, (void*)searchTerm)) {
fprintf(stderr, "Error creating thread\n");
return 1;
}
}
int rc;
for (i=0; i<threadsNumber; i++){
rc = pthread_join((threadsCollection[i]), NULL);
if(rc) {
fprintf(stderr, "Error joining thread, %d\n", rc);
return 1;
}
}
}
}
此代码使用线程从根搜索目录开始搜索名称包含 searchTerm 的文件。
【问题讨论】：
-
注意：在
isEmpty中：检查if (pQueue == NULL)应该返回true，好像没有队列，那么至少它是空的。 -
当队列中只有一项时检查
Dequeue操作。注意Enqueue中，当队列为空时，设置pQueue->head = pQueue->tail = item; -
在创建节点时你永远不会初始化指针 prev，因此它们的内容是不确定的，如果你取消引用它们，你会得到未定义的行为。可能不会导致这种情况，但仍然是一个问题。
-
错误是我之前的评论：item is not dequeued.
-
维护
size不是正确的方法：当头尾为空时队列为空。保持大小容易出错。