尝试将文件读入链接列表但程序在读取时崩溃

时间：2016-03-12 23:52:51

标签： c list malloc

我编写了一个程序，用于将文件中的一组数据读入链表。程序从文件中读取一行，对行进行标记，将其存储到节点中，然后移到下一行。每次执行此操作时，我都会打印节点的内容。我遇到的问题是，当程序运行时，它会停在文件中的两行之一并崩溃。它比另一条线更频繁地停在一条线上。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>

typedef struct prefectNode
{
    char *name; // prefect name
    char *type; // prefect type
    char *used;
    struct free// structure storing the prefect's free sessions on particular days
    {
        char M[9];
        char T[9];
        char W[9];
        char S[9];
        char F[9];
    } fses; // free sessions available to prefect;
    struct prefectNode *nextPtr;// a pointer to the next node
} pNode;// Self-Referential structure used to store information about a prefect
typedef pNode *ptrNode;// Synonym for a pointer to a self-referential structure

void induct(ptrNode *list, char l[]);// induct is called when information is being retrieved from file.

void induct(ptrNode *list, char l[])
{
    ptrNode curPtr = NULL;// pointer to the current node

    ptrNode newPtr = malloc(sizeof(pNode));// creating new node

    if (newPtr != NULL)
    {
        newPtr->name = strtok(l, ",");

        newPtr->type = strtok(NULL, ",");

        char *sesh = strtok(NULL, " ");
        char c = sesh[0];
        printf("%s\n%s\n", newPtr->name, newPtr->type);

        int i = 0, j = 0;
        for (i = 0; i < strlen(sesh); i++)
        {
            char c = sesh[i];
            if (c == 'M')
            {
                newPtr->fses.M[j] = sesh[i + 1];
                printf("M%c", newPtr->fses.M[j]);
            }
            if (c == 'T')
            {
                newPtr->fses.T[j] = sesh[i + 1];
                printf("T%c", newPtr->fses.T[j]);
            }
            if (c == 'W')
            {
                newPtr->fses.W[j] = sesh[i + 1];
                printf("W%c", newPtr->fses.W[j]);
            }
            if (c == 'S')
            {
                newPtr->fses.S[j] = sesh[i + 1];
                printf("S%c", newPtr->fses.S[j]);
            }
            if (c == 'F')
            {
                newPtr->fses.F[j] = sesh[i + 1];
                printf("F%c", newPtr->fses.F[j]);
            }

            i = i + 2;
            j++;
        }

        newPtr->nextPtr = NULL;
        curPtr = *list;

        if (curPtr == NULL)
        {
            newPtr->nextPtr = *list;
            *list = newPtr;
        }
        else
        {
            while (curPtr->nextPtr != NULL)
            {
                curPtr = curPtr->nextPtr;
            }
            curPtr->nextPtr = newPtr;
        }
    }
    else
    {
        printf("no memory");
    }
}

char ln[200];
FILE *fp;
int main()
{
    ptrNode start = NULL;

    fp = fopen("thefile.txt", "r");

    if (fp == NULL)
    {
        printf("File not found.");
    }
    else
    {
        while (!feof(fp))
        {
            fgets(ln, sizeof(ln), fp);
            induct(&start, ln);
            printf("\n\n");
        }
    }
    fclose(fp);
    getch();
    return 0;
}

这是输入文件的样本：

Denelia Alvaranga,R,M7_T4_T5_T6
Sainna Christian,R,M4_M5_M6_T1_T2_T3_F5_F6
Kashielle Clarke,R,F1_T4_W4_F4_T5_W5_S5_W6_S6_M7_W7
Candice Gordon,R,M1_M2_M3_S3_T7
Alphene Groves,R,M2_T5_S7_W3
T-Anna Johnson,R,M7
Vanessa Lewis,R,M1_M2_M3_S3_T4_W4_S4_T5_S5_T6_S6

当我到第9行时程序崩溃（更频繁）：

Rhoni-Ann Parkins,R,W1_S1_W2_S2_W3_S3_M4_T4_S4_F4_M5_T5_F5_M6_T6_F6_T7_F7

或第37行：

Ashleigh Graham,N6A

1 个答案:

答案 0 :(得分：0)

主要问题

您的一个主要问题是j失控 - 它在首次初始化后永远不会归零。 Rhoni-Ann因为她有很多自由时期而导致麻烦; Ashleigh因为没有空闲时间而导致麻烦。使用Rhoni-Ann，j达到18，但您索引的数组只能达到9.您需要重新访问代码的整个部分。您需要在日期字母后面读取该数字，并使用该数字代替j值。您还应验证该值是否足够小（值9将再次导致溢出;仅0..8即可），并报告日期字母无效。另请注意，分配内存时空间不归零。目前尚不清楚您之后会做什么，但您在M，T等数组中没有有效的字符串。

修订代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct prefectNode
{
    char *name; // prefect name
    char *type; // prefect type
    char *used;
    struct free// structure storing the prefect's free sessions on particular days
    {
        char M[9];
        char T[9];
        char W[9];
        char S[9];
        char F[9];
    } fses; // free sessions available to prefect;
    struct prefectNode *nextPtr;// a pointer to the next node
} pNode;// Self-Referential structure used to store information about a prefect
typedef pNode *ptrNode;// Synonym for a pointer to a self-referential structure

void induct(ptrNode *list, char l[]);// induct is called when information is being retrieved from file.

void induct(ptrNode *list, char l[])
{
    ptrNode curPtr = *list; // pointer to the current node
    ptrNode newPtr = calloc(sizeof(*newPtr), 1);// creating new node

    if (newPtr != NULL)
    {
        newPtr->name = strdup(strtok(l, ","));
        newPtr->type = strdup(strtok(NULL, ","));

        printf("Prefect: %s, type %s\n", newPtr->name, newPtr->type);

        char *sesh = strtok(NULL, " ");
        if (sesh == NULL)
        {
            fprintf(stderr, "No free sessions for %s\n", newPtr->name);
            free(newPtr->name);
            free(newPtr->type);
            free(newPtr);
            return;
        }

        int i = 0, j = 0;
        int len = strlen(sesh);
        for (i = 0; i < len; i++)
        {
            char c = sesh[i];
            if (c == 'M')
            {
                newPtr->fses.M[j] = sesh[i + 1];
                printf("M%c", newPtr->fses.M[j]);
            }
            if (c == 'T')
            {
                newPtr->fses.T[j] = sesh[i + 1];
                printf("T%c", newPtr->fses.T[j]);
            }
            if (c == 'W')
            {
                newPtr->fses.W[j] = sesh[i + 1];
                printf("W%c", newPtr->fses.W[j]);
            }
            if (c == 'S')
            {
                newPtr->fses.S[j] = sesh[i + 1];
                printf("S%c", newPtr->fses.S[j]);
            }
            if (c == 'F')
            {
                newPtr->fses.F[j] = sesh[i + 1];
                printf("F%c", newPtr->fses.F[j]);
            }
            printf("(j=%d)\n", j);

            i = i + 2;
            j++;
        }

        newPtr->nextPtr = NULL;
        curPtr = *list;

        if (curPtr == NULL)
        {
            newPtr->nextPtr = *list;
            *list = newPtr;
        }
        else
        {
            while (curPtr->nextPtr != NULL)
            {
                curPtr = curPtr->nextPtr;
            }
            curPtr->nextPtr = newPtr;
        }
    }
    else
    {
        printf("no memory\n");
    }
}

static void free_node(pNode *node)
{
    if (node != 0)
    {
        free(node->name);
        free(node->type);
        free(node);
    }
}

static void free_list(pNode *node)
{
    while (node != 0)
    {
        pNode *next = node->nextPtr;
        free_node(node);
        node = next;
    }
}

static void print_sessions(const char *dow, const char *ses)
{
    printf(" %s:", dow);
    for (int i = 0; i < 9; i++)
    {
        if (ses[i] != '\0')
            printf(" %c", ses[i]);
    }
}

static void print_node(const pNode *node)
{
    printf("%s [%s]", node->name, node->type);
    print_sessions("Mon", node->fses.M);
    print_sessions("Tue", node->fses.T);
    print_sessions("Wed", node->fses.W);
    print_sessions("Thu", node->fses.S);
    print_sessions("Fri", node->fses.F);
    putchar('\n');
}

static void print_list(const char *tag, pNode *list)
{
    printf("%s:\n", tag);
    while (list != NULL)
    {
        print_node(list);
        list = list->nextPtr;
    }
}

int main(void)
{
    FILE *fp;
    char ln[200];
    ptrNode start = NULL;
    const char filename[] = "thefile.txt";

    fp = fopen(filename, "r");

    if (fp == NULL)
    {
        fprintf(stderr, "File %s not found.\n", filename);
    }
    else
    {
        while (fgets(ln, sizeof(ln), fp) != 0)
        {
            size_t len = strlen(ln);
            if (len > 0)
                ln[len-1] = '\0';
            printf("[%s]\n", ln);
            induct(&start, ln);
        }
        fclose(fp);
        print_list("After data read", start);
        free_list(start);
    }

    return 0;
}

示例在valgrind

下运行 
==54054== Memcheck, a memory error detector
==54054== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==54054== Using Valgrind-3.12.0.SVN and LibVEX; rerun with -h for copyright info
==54054== Command: xyz
==54054== 
[Denelia Alvaranga,R,M7_T4_T5_T6]
Prefect: Denelia Alvaranga, type R
M7(j=0)
T4(j=1)
T5(j=2)
T6(j=3)
[Sainna Christian,R,M4_M5_M6_T1_T2_T3_F5_F6]
Prefect: Sainna Christian, type R
M4(j=0)
M5(j=1)
M6(j=2)
T1(j=3)
T2(j=4)
T3(j=5)
F5(j=6)
F6(j=7)
[Kashielle Clarke,R,F1_T4_W4_F4_T5_W5_S5_W6_S6_M7_W7]
Prefect: Kashielle Clarke, type R
F1(j=0)
T4(j=1)
W4(j=2)
F4(j=3)
T5(j=4)
W5(j=5)
S5(j=6)
W6(j=7)
S6(j=8)
M7(j=9)
W7(j=10)
[Candice Gordon,R,M1_M2_M3_S3_T7]
Prefect: Candice Gordon, type R
M1(j=0)
M2(j=1)
M3(j=2)
S3(j=3)
T7(j=4)
[Alphene Groves,R,M2_T5_S7_W3]
Prefect: Alphene Groves, type R
M2(j=0)
T5(j=1)
S7(j=2)
W3(j=3)
[T-Anna Johnson,R,M7]
Prefect: T-Anna Johnson, type R
M7(j=0)
[Vanessa Lewis,R,M1_M2_M3_S3_T4_W4_S4_T5_S5_T6_S6]
Prefect: Vanessa Lewis, type R
M1(j=0)
M2(j=1)
M3(j=2)
S3(j=3)
T4(j=4)
W4(j=5)
S4(j=6)
T5(j=7)
S5(j=8)
T6(j=9)
S6(j=10)
[Rhoni-Ann Parkins,R,W1_S1_W2_S2_W3_S3_M4_T4_S4_F4_M5_T5_F5_M6_T6_F6_T7_F7]
Prefect: Rhoni-Ann Parkins, type R
W1(j=0)
S1(j=1)
W2(j=2)
S2(j=3)
W3(j=4)
S3(j=5)
M4(j=6)
T4(j=7)
S4(j=8)
F4(j=9)
M5(j=10)
T5(j=11)
F5(j=12)
M6(j=13)
T6(j=14)
F6(j=15)
T7(j=16)
F7(j=17)
[Ashleigh Graham,N6A ]
Prefect: Ashleigh Graham, type N6A 
No free sessions for Ashleigh Graham
After data read:
Denelia Alvaranga [R] Mon: 7 Tue: 4 5 6 Wed: Thu: Fri:
Sainna Christian [R] Mon: 4 5 6 Tue: 1 2 3 Wed: Thu: Fri: 5 6
Kashielle Clarke [R] Mon: Tue: 7 4 5 Wed: 4 5 6 Thu: 7 5 6 Fri: 1 4
Candice Gordon [R] Mon: 1 2 3 Tue: 7 Wed: Thu: 3 Fri:
Alphene Groves [R] Mon: 2 Tue: 5 Wed: 3 Thu: 7 Fri:
T-Anna Johnson [R] Mon: 7 Tue: Wed: Thu: Fri:
Vanessa Lewis [R] Mon: 1 2 3 Tue: 4 5 Wed: 6 4 Thu: 3 4 5 Fri: 6
Rhoni-Ann Parkins [R] Mon: 4 Tue: 5 6 4 Wed: 1 5 3 6 7 Thu: 1 2 3 4 Fri:
==54054== 
==54054== HEAP SUMMARY:
==54054==     in use at exit: 26,297 bytes in 186 blocks
==54054==   total heap usage: 297 allocs, 111 frees, 37,503 bytes allocated
==54054== 
==54054== LEAK SUMMARY:
==54054==    definitely lost: 0 bytes in 0 blocks
==54054==    indirectly lost: 0 bytes in 0 blocks
==54054==      possibly lost: 0 bytes in 0 blocks
==54054==    still reachable: 0 bytes in 0 blocks
==54054==         suppressed: 26,297 bytes in 186 blocks
==54054== 
==54054== For counts of detected and suppressed errors, rerun with: -v
==54054== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

'抑制'内存是在Mac OS X（10.11.3）上运行的人工制品。我正在使用GCC 5.3.0。代码很干净 - 它释放它分配的所有内存。 （这就是'绝对丢失'，'间接丢失'，'可能丢失'，'仍然可达'的零点意味着。）

请注意，尽管使用valgrind，但它并没有抱怨“越界”内存访问，但是您可以看到j已打印并且对于Rhoni-Ann达到'j = 17'。你绝对不会写你想要的地方 - 每个知府的输出都不符合你的输入，因为j失控。当您在64位系统上将newPtr->fses.F[j]设置为j时写入17时，您仍然处于分配的内存范围内，因为struct free占用了nextPtr 45个字节，但填充到48个字节以对齐8字节指针F[17]，因此while (!feof(file))在指针内（您随后重写）。如果您使用32位编译器进行编译，则故事可能会有所不同。 （我得到了一些'有条件的跳转或移动取决于未初始化的值'错误，但没有按照我的预期写出“超出范围”。）

其他问题：

  • 请参阅[stderr总是错误的]，了解输入循环存在缺陷的原因。
  • 如果您无法打开文件，则不应尝试关闭该文件。
  • 您应该向stdout报告错误，而不是fp。
  • 您应该使用换行符结束消息，以便能够看到它们。
  • ln和main都应该是ln中的局部变量。
  • 您覆盖存储的名称，因为您没有复制包含在结构中的字符串 - 它们都指向数组used。
  • 您未将List<Integer> list1 = new LinkedList<>(Arrays.asList(11,22,33,44)); ListIterator<Integer> it = list1.listIterator(); while (it.hasNext()){ //version 1 System.out.println("value: " + it.next() + " index: " + it.nextIndex()); //version 2 System.out.println("index: " + it.nextIndex() + " value: " + it.next()); } 元素设置为已知值。
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