我实现了一个名为 myls 的简单版本的 ls,当我尝试释放程序中创建的链表时,我收到无效的 free() 通知,我认为这与 closedir() 有关,但我不知道不知道为什么,这里是内存泄漏检查:(***表示个人信息)
******:~/***/***/myls$ valgrind --leak-check=full --show-reachable=yes myls
==742== Memcheck, a memory error detector
==742== Copyright (C) 2002-2011, and GNU GPL'd, by Julian Seward et al.
==742== Using Valgrind-3.7.0 and LibVEX; rerun with -h for copyright info
==742== Command: myls
==742==
.
..
Makefile
myls
myls.c
tests
==742== Invalid free() / delete / delete[] / realloc()
==742== at 0x4C2A82E: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==742== by 0x4009D2: freeList (in /p2/hh/***/***/***/myls/myls)
==742== by 0x400AE2: main (in /p2/hh/***/***/***/myls/myls)
==742== Address 0x51f0083 is 67 bytes inside a block of size 32,816 alloc'd
==742== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==742== by 0x4EECD5A: __alloc_dir (opendir.c:202)
==742== by 0x400A0B: main (in /p2/hh/***/***/***/myls/myls)
==742==
==742==
==742== HEAP SUMMARY:
==742== in use at exit: 0 bytes in 0 blocks
==742== total heap usage: 7 allocs, 13 frees, 32,912 bytes allocated
==742==
==742== All heap blocks were freed -- no leaks are possible
==742==
==742== For counts of detected and suppressed errors, rerun with: -v
==742== ERROR SUMMARY: 6 errors from 1 contexts (suppressed: 2 from 2)
这是我的代码:
#include <stdio.h>
#include <dirent.h>
#include <stdlib.h>
#include <string.h>
typedef struct n{
char *key;
struct n *next;
} node;
node *list = NULL;
// errorCheck(*myDir) -- check if the target directory is opened
// correctly or print out an error message if not and exit.
void errorCheck(DIR *myDir){
if (myDir == NULL){
perror("Error");
exit(1);
}
}
// buildList(*myDir) -- create a list containing
// all directories' name.
node *buildList(DIR *myDir){
struct dirent *dirPtr;
node *temp = NULL;
// put into list
while ((dirPtr = readdir(myDir)) != NULL){
temp = malloc(sizeof(node));
if (temp == NULL){
fprintf(stderr, "Error: out of memory!\n");
exit(1);
}
temp -> key = dirPtr -> d_name;
temp -> next = list;
list = temp;
}
return temp;
}
// printList(*list) -- print out the linked list.
void printList(node *list){
node *temp = NULL;
temp = list;
while (temp != NULL){
printf("%s\n", temp -> key);
temp = temp -> next;
}
}
// swap(*n1, *n2) -- swap keys of these two nodes.
void swap(node *n1, node *n2){
char *temp;
temp = n1 -> key;
n1 -> key = n2 -> key;
n2 -> key = temp;
}
// sortList(*list) -- use bubble sort to sort the
// linked list in alphabetic order.
void sortList(node *list){
node *curr, *last = NULL;
int changed;
do{
changed = 0;
curr = list;
while (curr -> next != last){
if (strcmp(curr -> key, curr -> next -> key) > 0){
swap(curr, curr -> next);
changed = 1;
}
curr = curr -> next;
}
last = curr;
} while (changed == 1);
}
// freeList() -- free up the linked list.
void freeList(){
node *temp = list;
while (list != NULL){
temp = list;
list = list -> next;
free(temp -> key);
free(temp);
}
}
// main() -- main structure of the program
int main(int argc, char *argv[]){
DIR *myDir;
if (argc == 1){
myDir = opendir(".");
errorCheck(myDir);
list = buildList(myDir);
sortList(list);
printList(list);
closedir(myDir);
}
else if(argc == 2){
myDir = opendir(argv[1]);
errorCheck(myDir);
list = buildList(myDir);
sortList(list);
printList(list);
closedir(myDir);
}
else{
fprintf(stderr, "Error: too many arguments!\n");
return 1;
}
freeList();
return 0;
}
有人能帮忙吗?
最佳答案
我没有明确地看到 temp->key 的内存分配在哪里,所以我猜你不应该在上面调用 free()。
// freeList() -- free up the linked list.
void freeList(){
node *temp = list;
while (list != NULL){
temp = list;
list = list -> next;
**free(temp -> key);**
free(temp);
}
信息来自:http://man7.org/linux/man-pages/man3/readdir.3.html
On success, readdir() returns a pointer to a dirent structure. (This
structure may be statically allocated; do not attempt to free(3) it.)
关于c - closedir() 后无效的 free(),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/36366951/