用C链表内存泄漏 [英] Memory Leaks in C Linked List
本文介绍了用C链表内存泄漏的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我一直工作在学校的一个项目（由于今晚！），和我有一些严重的内存问题。我是相当新的C和我仍然被抛出了一个循环，当谈到mallocing指针和诸如此类的东西，所以我真的可以使用一些帮助。
在code如下。该文件的顺序是LinkedLists.h（标题为链表模块），LinkedLists.c（链表模块），和TestList.c（主模块）。
/ ********* *****************************************
*基础结构包含数据结构元素信息：由deterimined
*应用程序需要。
************************************************** ************ /
的#ifndef _LINKED_LISTS_H_
＃定义_LINKED_LISTS_H_typedef结构ElementStructs
{
INT ElementPosition;
字符* ElementValue;
} ElementStructs;/ **************没有别的模块中需要修改************* // ******************* *****************************
*列表中的节点的结构基础，包含用户信息和链接指针。
*该ElementStructstypemark必须定义根据的具体需要
*应用程序。
************************************************** ************ /
typedef结构LinkedListNodes
{
/ *用户信息字段* /
ElementStructs * ElementPtr;
/ *链接指针* /
结构LinkedListNodes *下一步;
结构LinkedListNodes * previous;
} LinkedListNodes;/ ******************* *****************************
*基础结构用于管理链表数据结构。
************************************************** ************ /
typedef结构LinkedLists
{
/ *列表中的元素数* /
INT numElements个;
/ *指向元素列表的前面，可能为NULL * /
结构LinkedListNodes * FrontPtr;
/ *指向元素列表的末尾，可能为NULL * /
结构LinkedListNodes * BackPtr;
} LinkedLists;/ ******************* *****************************
*初始化链表数据结构
************************************************** ************ /
无效InitLinkedList（LinkedLists * ListPtr）;/ ******************* *****************************
*将记录添加到列表的前面。
************************************************** ************ /
无效AddToFrontOfLinkedList（LinkedLists * ListPtr，ElementStructs * DataPtr）;/ ******************* *****************************
*将记录添加到列表的后面。
************************************************** ************ /
无效AddToBackOfLinkedList（LinkedLists * ListPtr，ElementStructs * DataPtr）;/ ******************* *****************************
*删除（返回）从列表中的前一个记录（作品甚至在
*通过返回NULL一个空列表）。
************************************************** ************ /
ElementStructs * RemoveFromFrontOfLinkedList（LinkedLists * ListPtr）;/ ******************* *****************************
*移除（和返回）从列表的背面的记录（作品，即使上
*通过返回NULL一个空列表）。
************************************************** ************ /
ElementStructs * RemoveFromBackOfLinkedList（LinkedLists * ListPtr）;/ ******************* *****************************
*德分配链表并复位结构字段仿佛
*列表是空的。
************************************************** ************ /
无效DestroyLinkedList（LinkedLists * ListPtr）;#ENDIF / * * _LINKED_LISTS_H_ /
LinkedLists.c：
/ ********* *****************************************
*提取并打印从指定数据的第一个和最后6个元素
*设置并打印在输入文件中的单词的总数。利用
在LinkedLists.h指定* LinkedList的模块
*通过书面XXXXXXX
************************************************** ************ /
＃包括LT＆;＆stdio.h中GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LinkedLists.h无效InitLinkedList（LinkedLists * ListPtr）
{
ListPtr-＆GT; numElements个= 0;
ListPtr-＆GT; FrontPtr = NULL;
ListPtr-＆GT; BackPtr = NULL;
}无效AddToFrontOfLinkedList（LinkedLists * ListPtr，ElementStructs
* DataPtr）
{ / *如果没有其他元素，创造新的节点，并添加它，
*将其分配给这两个前和后的指针* /
如果（ListPtr-＆GT; numElements个== 0）
{
ListPtr-＆GT; FrontPtr =的malloc（sizeof的（LinkedListNodes））;
ListPtr-＆GT; FrontPtr-＆GT; ElementPtr = DataPtr;
ListPtr-＆GT; FrontPtr-＆gt;接着= NULL;
ListPtr-＆GT; FrontPtr-＆GT; previous = NULL;
ListPtr-＆GT; BackPtr = ListPtr-＆GT; FrontPtr;
} / *如果有其他的元素，创建新节点并把它添加到前
*同时保留previous节点顺序* /
其他
{
/ *初始化新的一个LinkedListNode * /
ListPtr-＆GT; FrontPtr-＆GT; previous =的malloc（sizeof的（LinkedListNodes））;
ListPtr-＆GT; FrontPtr-＆GT; previous-＆GT; ElementPtr = DataPtr;
ListPtr-＆GT; FrontPtr-＆GT; previous-＆gt;接下来= ListPtr-＆GT; FrontPtr;
ListPtr-＆GT; FrontPtr-＆GT; previous-＆GT; previous = NULL; / *指定新初始化的节点作为链表的前面节点* /
ListPtr-＆GT; FrontPtr = ListPtr-＆GT; FrontPtr-＆GT; previous;
} / *列表大小加1 * /
（ListPtr-＆GT; numElements个）++;
}无效AddToBackOfLinkedList（LinkedLists * ListPtr，ElementStructs
* DataPtr）
{
/ *如果没有其他元素，创造新的节点，并添加它，
*将其分配给这两个前和后的指针* /
如果（ListPtr-＆GT; numElements个== 0）
{
ListPtr-＆GT; FrontPtr =的malloc（sizeof的（LinkedListNodes））;
ListPtr-＆GT; FrontPtr-＆GT; ElementPtr = DataPtr;
ListPtr-＆GT; FrontPtr-＆gt;接着= NULL;
ListPtr-＆GT; FrontPtr-＆GT; previous = NULL;
ListPtr-＆GT; BackPtr = ListPtr-＆GT; FrontPtr;
/ *的printf（添加％s \\ n，DataPtr-＆GT; ElementValue）; * /
} / *如果有其他的元素，创建新节点并把它添加到后面
*同时保留previous节点顺序* /
其他
{
/ *初始化新的一个LinkedListNode * /
ListPtr-＆GT; BackPtr-＆gt;接着= malloc的（的sizeof（LinkedListNodes））;
ListPtr-＆GT; BackPtr-＆GT;下一步 - ＆GT; ElementPtr = DataPtr;
ListPtr-＆GT; BackPtr-＆GT;下一步 - ＆GT; previous = ListPtr-＆GT; BackPtr;
ListPtr-＆GT; BackPtr-＆GT;下一步 - ＆GT; previous = ListPtr-＆GT; BackPtr;
ListPtr-＆GT; BackPtr-＆GT;下一步 - ＆gt;接着= NULL; / *指定新初始化节点的LinkedList的背面节点* /
ListPtr-＆GT; BackPtr = ListPtr-＆GT; BackPtr-＆gt;接下来，
的printf（添加％s \\ n，ListPtr-＆GT; BackPtr-＆GT; ElementPtr-＆GT; ElementValue）;
} / *列表大小加1 * /
（ListPtr-＆GT; numElements个）++;
}ElementStructs * RemoveFromFrontOfLinkedList（LinkedLists * ListPtr）
{
如果（ListPtr-＆GT; numElements个大于0）
{
ElementStructs * removedElement = ListPtr-＆GT; FrontPtr-＆GT; ElementPtr;
LinkedListNodes * removedNode = ListPtr-＆GT; FrontPtr;
如果（ListPtr-＆GT; numElements个== 1）
{
ListPtr-＆GT; FrontPtr = NULL;
}
其他
{
ListPtr-＆GT; FrontPtr = ListPtr-＆GT; FrontPtr-＆gt;接下来，
ListPtr-＆GT; FrontPtr-＆GT; previous = NULL;
}
（ListPtr-＆GT; numElements个） - ;
免费（removedNode）;
返回removedElement;
}
其他
{
ElementStructs * nullElement = NULL;
返回nullElement;
}
}ElementStructs * RemoveFromBackOfLinkedList（LinkedLists * ListPtr）
{
如果（ListPtr-＆GT; numElements个→1）
{
ElementStructs * removedElement = ListPtr-＆GT; BackPtr-＆GT; ElementPtr;
LinkedListNodes * removedNode = ListPtr-＆GT; BackPtr;
如果（ListPtr-＆GT; numElements个== 1）
{
ListPtr-＆GT; BackPtr = NULL;
}
其他
{
ListPtr-＆GT; BackPtr = ListPtr-＆GT; BackPtr-＆GT; previous;
ListPtr-＆GT; BackPtr-＆gt;接着= NULL;
}
（ListPtr-＆GT; numElements个） - ;
免费（removedNode）;
返回removedElement;
}
其他
{
ElementStructs * nullElement = NULL;
返回nullElement;
}
}
无效DestroyLinkedList（LinkedLists * ListPtr）
{
而（ListPtr-＆GT;！FrontPtr = NULL）
{
LinkedListNodes * removedNode = ListPtr-＆GT; FrontPtr;
ListPtr-＆GT; FrontPtr = ListPtr-＆GT; FrontPtr-＆gt;接下来， / *在节点取消分配单元* /
免费（removedNode-＆GT; ElementPtr-＆GT; ElementValue）;
免费（removedNode-＆GT; ElementPtr）; / *解除分配节点* /
免费（removedNode）;
}
免费（ListPtr）;
}
TestList.c：
/ ********* *****************************************
*测试用LinkedLists.h指定的链表的功能
*文件美式英语的话。读取单个单词，并将它们存储
*如在LinkedList的节点元素。
*通过书面XXXXX
************************************************** *************************** /
＃包括LT＆;＆stdio.h中GT;
＃包括LT＆;＆stdlib.h中GT;
＃包括LT＆;＆string.h中GT;
＃包括LinkedLists.hMAX_LENGTH的#define 100 / *中的任何专业英语词典*最长的单词长度/INT主（INT ARGC，字符**参数）
{
如果（的argc == 2）
{
/ *初始化链表* /
LinkedLists * LL; / *文件指针输入文件* /
FILE * FP; / *节点从文件存储*输入数据/
ElementStructs * NODEDATA; / *循环完成布尔* /
诠释完成; / *循环位置计数器* /
INT位置; / * *迭代器/
ElementStructs * CurElement; / *打开输入文件，并检查它是可读的。如果不是，退出* /
FP = FOPEN（参数[1]，R）; 如果（FP == NULL）
{
fprintf中（标准错误，文件打开失败。）;
返回2;
} / *初始化链表和其它必要的变量* /
LL =的malloc（sizeof的（* LL））;
InitLinkedList（LL）; 完成= 0;
位置= 0; 做
{
如果（！的feof（FP））
{
/ *分配空间的新节点的数据* /
NODEDATA =的malloc（sizeof的（ElementStructs））; / *分配的节点元素的空间输入字符串* /
NodeData-＆GT; ElementValue =的malloc（MAX_LENGTH *的sizeof（字符））; 从文件* / *读取新节点的数据/
的fscanf（FP，％S，NodeData-＆GT; ElementValue）; / *指定扫描值节点单元* /
NodeData-＆GT; ElementPosition =位置;
/ *的strcpy（NodeData-＆GT; ElementValue，readString）; * / / *数据节点添加到链表* /
AddToFrontOfLinkedList（LL，NODEDATA）;
}
其他
DONE = 1;
位置++;
}而（完成== 0）; 做
{
CurElement = RemoveFromFrontOfLinkedList（LL）; 如果（CurElement！= NULL）
的printf（字＃％D：％S \\ n，CurElement-＆GT; ElementPosition，
CurElement-＆GT; ElementValue）;
}而（CurElement！= NULL）; / *解除分配链表* /
DestroyLinkedList（LL）;
FCLOSE（FP）; }
/ *错误的命令行输入* /
其他
{
fprintf中（标准错误，不正确数量的参数）;
返回1;
} 返回0;
}
程序编译罚款。但是，运行它会导致在执行的最后一个赛格故障，并报告Valgrind的多个内存泄漏（如下图所示）。请，如果您有任何帮助提供，我将非常感谢。这个问题主要是在LinkedList.c模块中的RemoveFromBackOfLinkedList和RemoveFromFrontOfLinkedList方法。有code的主模块（TestList.c）调用这些函数在块（我都试过，但它们有几乎相同的功能，也不工作）。块是做/同时显示如下循环：
做
{
CurElement = RemoveFromFrontOfLinkedList（LL）; 如果（CurElement！= NULL）
的printf（字＃％D：％S \\ n，CurElement-＆GT; ElementPosition，
CurElement-＆GT; ElementValue）;
}而（CurElement！= NULL）;
Valgrind的结果：
字＃225921：化学计量
。
。
。
。
字＃6：凸轮
字＃5：石化的
字＃4：万亿
字＃3：祝福
字＃2：wisted
字＃1：毒素
== == 4849尺寸为8的写入无效
== == 4849在0x400B5C：RemoveFromFrontOfLinkedList（在/ home / amb2189 / HW3 / TestList）
== == 4849通过0x40085B：主（在/ home / amb2189 / HW3 / TestList）
== == 4849地址为0x10不stack'd，malloc分配或（最近）free'd
== == 4849
== == 4849
== == 4849过程终止与信号11的默认操作（SIGSEGV）
== == 4849地址为0x10不映射区域内访问
== == 4849在0x400B5C：RemoveFromFrontOfLinkedList（在/ home / amb2189 / HW3 / TestList）
== == 4849通过0x40085B：主（在/ home / amb2189 / HW3 / TestList）
== == 4849如果你认为发生这种情况作为一个堆栈的结果
== == 4849溢出程序的主线程（不可能的，但
== == 4849可能），你可以尝试增加的大小
== == 4849用 - 主 - STACKSIZE =标志主线程堆栈。
== == 4849在这个运行中所用的主线程的堆栈大小是8388608。
== == 4849
== == 4849 HEAP摘要：
== == 4849使用在出口处：在413185块23965172字节
== == 4849总堆的使用情况：619775 allocs，206590的FreeS，28923332字节分配
== == 4849
== == 4849在16块1个字节可能迷失在负的战绩1 9
== == 4849在0x4C2B6CD：的malloc（以/usr/lib/valgrind/vg$p$pload_memcheck-amd64-linux.so）
== == 4849通过0x4007E2：主（在/ home / amb2189 / HW3 / TestList）
== == 4849
== == 4849 200 2块字节可能迷失在负的战绩5 9
== == 4849在0x4C2B6CD：的malloc（以/usr/lib/valgrind/vg$p$pload_memcheck-amd64-linux.so）
== == 4849通过0x4007F0：主（在/ home / amb2189 / HW3 / TestList）
== == 4849
== == 4849 23963992（3305392直接，间接20658600）字节206587块9的9负的战绩肯定是丢
== == 4849在0x4C2B6CD：的malloc（以/usr/lib/valgrind/vg$p$pload_memcheck-amd64-linux.so）
== == 4849通过0x4007E2：主（在/ home / amb2189 / HW3 / TestList）
== == 4849
== == 4849泄漏摘要：
== == 4849肯定丢失：3305392字节206587块
== == 4849失去了间接的：20658600字节206586块
== == 4849可能丢失：216字节的3个街区
== == 4849到达尚：在9块964字节
== == 4849燮pressed：0字节0块
== 4849 ==可达块（那些其中指针被发现）未示出。
== == 4849要查看它们，重新运行：--leak检查=全--show-可达= YES
== == 4849
== == 4849对于检测燮pressed错误计数，重新运行：-v
== == 4849使用--track-起源= yes来看到未初始化值来自
== == 4849错误摘要：从5环境5个错误（SUP pressed：2 2）
分段错误（核心转储）
解决方案
请一些变化在2删除等功能,,
ElementStructs * RemoveFromFrontOfLinkedList（LinkedLists * ListPtr）
{
如果（ListPtr-＆GT; numElements个大于0）
{
/ * * ElementStructs = removedElement＆ListPtr- GT; FrontPtr-＆GT; ElementPtr; * /
/ * * LinkedListNodes = removedNode的malloc（sizeof的（removedNode））; //无需进行分配，因为要删除的节点
removedNode = ListPtr-＆GT; FrontPtr; * /
LinkedListNodes * removedNode = ListPtr-＆GT; FrontPtr; //使用这行
ListPtr-＆GT; FrontPtr = ListPtr-＆GT; FrontPtr-＆gt;接下来，
ListPtr-＆GT; FrontPtr-＆GT; previous = NULL;
免费（removedNode）;
（ListPtr-＆GT; numElements个） - ;
返回NULL;
}
其他
{
ElementStructs * nullElement = NULL;
返回nullElement;
}
}ElementStructs * RemoveFromBackOfLinkedList（LinkedLists * ListPtr）
{
如果（ListPtr-＆GT;！numElements个= 0）
{
ElementStructs * removedElement = ListPtr-＆GT; BackPtr-＆GT; ElementPtr;
LinkedListNodes * removedNode = ListPtr-＆GT; BackPtr;
ListPtr-＆GT; BackPtr = ListPtr-＆GT; BackPtr-＆GT; previous;
ListPtr-＆GT; BackPtr-＆gt;接着= NULL;
免费（removedNode）;
（ListPtr-＆GT; numElements个） - ; //添加此行
返回removedElement;
}
其他
{
ElementStructs * nullElement = NULL;
返回nullElement;
}
}
修改1
CurElement =的malloc（sizeof的（* CurElement））; 这是另一个MEM-泄漏主，你不必使用malloc它，只是删除此行。
编辑2：你为什么不释放你的元素和ELEMENTVALUE ...
做
{
CurElement = RemoveFromFrontOfLinkedList（LL）; 如果（CurElement！= NULL）{
的printf（字＃％D：％S \\ n，CurElement-＆GT; ElementPosition，
CurElement-＆GT; ElementValue）;
免费（CurElement-＆GT; ElementValue）; //添加这些2号线释放ELEMENTVALUE和元素。
免费（CurElement）;
}
}而（CurElement！= NULL）;
I've been working on a project for school (Due tonight!), and I'm having some serious memory issues. I'm fairly new to C and am still being thrown for a loop when it comes to mallocing pointers and whatnot, so I could really use some help.
The code is as follows. The order of the files is LinkedLists.h (Header for LinkedList module), LinkedLists.c (LinkedList module), and TestList.c (Main module).
/******************************************************************************
* Base struct to contain data structure element information: deterimined by
* the application needs.
******************************************************************************/
#ifndef _LINKED_LISTS_H_
#define _LINKED_LISTS_H_
typedef struct ElementStructs
{
int ElementPosition;
char* ElementValue;
} ElementStructs;
/************** Nothing else in the module needs to be modified *************/
/******************************************************************************
* Base struct of list nodes, contains user information and link pointers.
* The "ElementStructs" typemark must be defined based on specific needs of the
* application.
******************************************************************************/
typedef struct LinkedListNodes
{
/* The user information field */
ElementStructs *ElementPtr;
/* Link pointers */
struct LinkedListNodes *Next;
struct LinkedListNodes *Previous;
} LinkedListNodes;
/******************************************************************************
* Base struct used to manage the linked list data structure.
******************************************************************************/
typedef struct LinkedLists
{
/* Number of elements in the list */
int NumElements;
/* Pointer to the front of the list of elements, possibly NULL */
struct LinkedListNodes *FrontPtr;
/* Pointer to the end of the list of elements, possibly NULL */
struct LinkedListNodes *BackPtr;
} LinkedLists;
/******************************************************************************
* Initialized the linked list data structure
******************************************************************************/
void InitLinkedList(LinkedLists *ListPtr);
/******************************************************************************
* Adds a record to the front of the list.
******************************************************************************/
void AddToFrontOfLinkedList(LinkedLists *ListPtr, ElementStructs *DataPtr);
/******************************************************************************
* Adds a record to the back of the list.
******************************************************************************/
void AddToBackOfLinkedList(LinkedLists *ListPtr, ElementStructs *DataPtr);
/******************************************************************************
* Removes (and returns) a record from the front of the list ('works' even on
* an empty list by returning NULL).
******************************************************************************/
ElementStructs *RemoveFromFrontOfLinkedList(LinkedLists *ListPtr);
/******************************************************************************
* Removes (and returns) a record from the back of the list ('works' even on
* an empty list by returning NULL).
******************************************************************************/
ElementStructs *RemoveFromBackOfLinkedList(LinkedLists *ListPtr);
/******************************************************************************
* De-allocates the linked list and resets the struct fields as if the
* list was empty.
******************************************************************************/
void DestroyLinkedList(LinkedLists *ListPtr);
#endif /* _LINKED_LISTS_H_ */
LinkedLists.c:
/******************************************************************************
* Extracts and prints the first and last 6 elements from the specified data
* set and prints the total number of words in the input file. Utilizes the
* LinkedList module as specified in LinkedLists.h
* Written by xxxxxxx
******************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include "LinkedLists.h"
void InitLinkedList(LinkedLists *ListPtr)
{
ListPtr->NumElements = 0;
ListPtr->FrontPtr = NULL;
ListPtr->BackPtr = NULL;
}
void AddToFrontOfLinkedList(LinkedLists *ListPtr, ElementStructs
*DataPtr)
{
/* If there are no other elements, create new node and add it,
* assigning it to both the front and back pointers */
if(ListPtr->NumElements == 0)
{
ListPtr->FrontPtr = malloc(sizeof(LinkedListNodes));
ListPtr->FrontPtr->ElementPtr = DataPtr;
ListPtr->FrontPtr->Next = NULL;
ListPtr->FrontPtr->Previous = NULL;
ListPtr->BackPtr = ListPtr->FrontPtr;
}
/* If there are other elements, create new node and add it to the front
* while retaining previous node order */
else
{
/* Initialize new LinkedListNode */
ListPtr->FrontPtr->Previous = malloc(sizeof(LinkedListNodes));
ListPtr->FrontPtr->Previous->ElementPtr = DataPtr;
ListPtr->FrontPtr->Previous->Next = ListPtr->FrontPtr;
ListPtr->FrontPtr->Previous->Previous = NULL;
/* Assign newly initialized node as front node of LinkedList */
ListPtr->FrontPtr = ListPtr->FrontPtr->Previous;
}
/* List size plus one */
(ListPtr->NumElements)++;
}
void AddToBackOfLinkedList(LinkedLists *ListPtr, ElementStructs
*DataPtr)
{
/* If there are no other elements, create new node and add it,
* assigning it to both the front and back pointers */
if(ListPtr->NumElements == 0)
{
ListPtr->FrontPtr = malloc(sizeof(LinkedListNodes));
ListPtr->FrontPtr->ElementPtr = DataPtr;
ListPtr->FrontPtr->Next = NULL;
ListPtr->FrontPtr->Previous = NULL;
ListPtr->BackPtr = ListPtr->FrontPtr;
/*printf("Adding %s\n", DataPtr->ElementValue);*/
}
/* If there are other elements, create new node and add it to the back
* while retaining previous node order */
else
{
/* Initialize new LinkedListNode */
ListPtr->BackPtr->Next = malloc(sizeof(LinkedListNodes));
ListPtr->BackPtr->Next->ElementPtr = DataPtr;
ListPtr->BackPtr->Next->Previous = ListPtr->BackPtr;
ListPtr->BackPtr->Next->Previous = ListPtr->BackPtr;
ListPtr->BackPtr->Next->Next = NULL;
/* Assign newly initialized node as back node of LinkedList */
ListPtr->BackPtr = ListPtr->BackPtr->Next;
printf("Adding %s\n", ListPtr->BackPtr->ElementPtr->ElementValue);
}
/* List size plus one */
(ListPtr->NumElements)++;
}
ElementStructs *RemoveFromFrontOfLinkedList(LinkedLists *ListPtr)
{
if(ListPtr->NumElements > 0)
{
ElementStructs *removedElement = ListPtr->FrontPtr->ElementPtr;
LinkedListNodes *removedNode = ListPtr->FrontPtr;
if(ListPtr->NumElements == 1)
{
ListPtr->FrontPtr = NULL;
}
else
{
ListPtr->FrontPtr = ListPtr->FrontPtr->Next;
ListPtr->FrontPtr->Previous = NULL;
}
(ListPtr->NumElements)--;
free(removedNode);
return removedElement;
}
else
{
ElementStructs *nullElement = NULL;
return nullElement;
}
}
ElementStructs *RemoveFromBackOfLinkedList(LinkedLists *ListPtr)
{
if(ListPtr->NumElements > 1)
{
ElementStructs *removedElement = ListPtr->BackPtr->ElementPtr;
LinkedListNodes *removedNode = ListPtr->BackPtr;
if(ListPtr->NumElements == 1)
{
ListPtr->BackPtr = NULL;
}
else
{
ListPtr->BackPtr = ListPtr->BackPtr->Previous;
ListPtr->BackPtr->Next = NULL;
}
(ListPtr->NumElements)--;
free(removedNode);
return removedElement;
}
else
{
ElementStructs *nullElement = NULL;
return nullElement;
}
}
void DestroyLinkedList(LinkedLists *ListPtr)
{
while(ListPtr->FrontPtr != NULL)
{
LinkedListNodes *removedNode = ListPtr->FrontPtr;
ListPtr->FrontPtr = ListPtr->FrontPtr->Next;
/* Deallocate element in node */
free(removedNode->ElementPtr->ElementValue);
free(removedNode->ElementPtr);
/* Deallocate node */
free(removedNode);
}
free(ListPtr);
}
TestList.c:
/******************************************************************************
* Tests the functionality of the LinkedList specified in LinkedLists.h using
* the file "american-english-words". Reads in individual words and stores them
* as node elements in the LinkedList.
* Written by xxxxx
*****************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "LinkedLists.h"
#define MAX_LENGTH 100 /* Length of longest word in any major English dictionary */
int main(int argc, char** args)
{
if(argc == 2)
{
/* Initialize LinkedList */
LinkedLists *LL;
/* File pointer to input file */
FILE *fp;
/* Node to store input data from file */
ElementStructs *NodeData;
/* Loop completion boolean */
int Done;
/* Loop position counter */
int Position;
/* Iterator */
ElementStructs *CurElement;
/* Open input file and check that it is readable. If not, exit */
fp = fopen(args[1], "r");
if(fp == NULL)
{
fprintf(stderr, "File open failed.");
return 2;
}
/* Initialize linked list and other necessary variables */
LL = malloc(sizeof(*LL));
InitLinkedList(LL);
Done = 0;
Position = 0;
do
{
if(!feof(fp))
{
/* Allocate space for new node data */
NodeData = malloc(sizeof(ElementStructs));
/* Allocate space in node element for input string */
NodeData->ElementValue = malloc(MAX_LENGTH * sizeof(char));
/* Read new node data from file */
fscanf(fp, "%s", NodeData->ElementValue);
/* Assign scanned values to node elements */
NodeData->ElementPosition = Position;
/*strcpy(NodeData->ElementValue, readString);*/
/* Add data node to LinkedList */
AddToFrontOfLinkedList(LL, NodeData);
}
else
Done = 1;
Position++;
}while(Done == 0);
do
{
CurElement = RemoveFromFrontOfLinkedList(LL);
if(CurElement != NULL)
printf("Word #%d: %s\n", CurElement->ElementPosition,
CurElement->ElementValue);
}while(CurElement != NULL);
/* Deallocate linked list */
DestroyLinkedList(LL);
fclose(fp);
}
/* Bad command line input */
else
{
fprintf(stderr, "Incorrect number of arguments");
return 1;
}
return 0;
}
The program compiles fine. However, running it causes a seg fault at the end of execution, and valgrind reports multiple memory leaks (Shown below). Please, if you have any help to offer, I would be extremely grateful. The issue is mostly in the RemoveFromBackOfLinkedList and RemoveFromFrontOfLinkedList methods in the LinkedList.c module. There's a block of code in the main module (TestList.c) that calls one of these functions (I've tried both, but they have nearly identical functionality, and neither works). The block is a do/while loop shown below:
do
{
CurElement = RemoveFromFrontOfLinkedList(LL);
if(CurElement != NULL)
printf("Word #%d: %s\n", CurElement->ElementPosition,
CurElement->ElementValue);
}while(CurElement != NULL);
Valgrind Results:
Word #225921: stoich
.
.
.
.
Word #6: Cam's
Word #5: petrochemistry's
Word #4: Tera
Word #3: benedictions
Word #2: wisted
Word #1: toxins
==4849== Invalid write of size 8
==4849== at 0x400B5C: RemoveFromFrontOfLinkedList (in /home/amb2189/hw3/TestList)
==4849== by 0x40085B: main (in /home/amb2189/hw3/TestList)
==4849== Address 0x10 is not stack'd, malloc'd or (recently) free'd
==4849==
==4849==
==4849== Process terminating with default action of signal 11 (SIGSEGV)
==4849== Access not within mapped region at address 0x10
==4849== at 0x400B5C: RemoveFromFrontOfLinkedList (in /home/amb2189/hw3/TestList)
==4849== by 0x40085B: main (in /home/amb2189/hw3/TestList)
==4849== If you believe this happened as a result of a stack
==4849== overflow in your program's main thread (unlikely but
==4849== possible), you can try to increase the size of the
==4849== main thread stack using the --main-stacksize= flag.
==4849== The main thread stack size used in this run was 8388608.
==4849==
==4849== HEAP SUMMARY:
==4849== in use at exit: 23,965,172 bytes in 413,185 blocks
==4849== total heap usage: 619,775 allocs, 206,590 frees, 28,923,332 bytes allocated
==4849==
==4849== 16 bytes in 1 blocks are possibly lost in loss record 1 of 9
==4849== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4849== by 0x4007E2: main (in /home/amb2189/hw3/TestList)
==4849==
==4849== 200 bytes in 2 blocks are possibly lost in loss record 5 of 9
==4849== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4849== by 0x4007F0: main (in /home/amb2189/hw3/TestList)
==4849==
==4849== 23,963,992 (3,305,392 direct, 20,658,600 indirect) bytes in 206,587 blocks are definitely lost in loss record 9 of 9
==4849== at 0x4C2B6CD: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==4849== by 0x4007E2: main (in /home/amb2189/hw3/TestList)
==4849==
==4849== LEAK SUMMARY:
==4849== definitely lost: 3,305,392 bytes in 206,587 blocks
==4849== indirectly lost: 20,658,600 bytes in 206,586 blocks
==4849== possibly lost: 216 bytes in 3 blocks
==4849== still reachable: 964 bytes in 9 blocks
==4849== suppressed: 0 bytes in 0 blocks
==4849== Reachable blocks (those to which a pointer was found) are not shown.
==4849== To see them, rerun with: --leak-check=full --show-reachable=yes
==4849==
==4849== For counts of detected and suppressed errors, rerun with: -v
==4849== Use --track-origins=yes to see where uninitialised values come from
==4849== ERROR SUMMARY: 5 errors from 5 contexts (suppressed: 2 from 2)
Segmentation fault (core dumped)
解决方案
Make some changes in your 2 delete functions,,
ElementStructs *RemoveFromFrontOfLinkedList(LinkedLists *ListPtr)
{
if(ListPtr->NumElements > 0)
{
/* ElementStructs *removedElement = ListPtr->FrontPtr->ElementPtr;*/
/*LinkedListNodes *removedNode = malloc(sizeof(removedNode)); // no need allocate because you are deleting the node
removedNode = ListPtr->FrontPtr;*/
LinkedListNodes *removedNode = ListPtr->FrontPtr; // use this line
ListPtr->FrontPtr = ListPtr->FrontPtr->Next;
ListPtr->FrontPtr->Previous = NULL;
free(removedNode);
(ListPtr->NumElements)--;
return NULL;
}
else
{
ElementStructs *nullElement = NULL;
return nullElement;
}
}
ElementStructs *RemoveFromBackOfLinkedList(LinkedLists *ListPtr)
{
if(ListPtr->NumElements != 0)
{
ElementStructs *removedElement = ListPtr->BackPtr->ElementPtr;
LinkedListNodes *removedNode = ListPtr->BackPtr;
ListPtr->BackPtr = ListPtr->BackPtr->Previous;
ListPtr->BackPtr->Next = NULL;
free(removedNode);
(ListPtr->NumElements)--; // add this line
return removedElement;
}
else
{
ElementStructs *nullElement = NULL;
return nullElement;
}
}
EDIT 1
CurElement = malloc(sizeof(*CurElement)); this is another mem-leak in main, you don't have to use malloc for it, just remove this line.
EDIT 2: Why aren't you freeing your ELEMENT and ELEMENTVALUE...?
do
{
CurElement = RemoveFromFrontOfLinkedList(LL);
if(CurElement != NULL) {
printf("Word #%d: %s\n", CurElement->ElementPosition,
CurElement->ElementValue);
free(CurElement->ElementValue); //add these 2 line to free ELEMENTVALUE And ELEMENT.
free(CurElement);
}
}while(CurElement != NULL);
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