c - 为什么我会遇到段错误:以下程序中的11

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想改进这个问题吗？Update the question所以堆栈溢出的值小于aa>。
去年关门了。
我有切分错误：11
运行菜单/命令后，我想将输入添加到列表中。想弄清楚但我无能为力

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>
#define MAX_LENGTH 1023

//**********************************************************************
//  Linked List Definitions
//  Define your linked list node and pointer types
//  here for use throughout the file.
//
//   ADD STATEMENT(S) HERE
typedef struct contact
{
    char familyName[MAX_LENGTH+1];
    char firstName[MAX_LENGTH+1];
    char address[MAX_LENGTH+1];
    char phoneNumber[MAX_LENGTH+1];
    struct contact *link;
//pointer to next node.
} contact;
//**********************************************************************
// Linked List Function Declarations
//
// Functions that modify the linked list.
//   Declare your linked list functions here.
//
//   ADD STATEMENT(S) HERE
//**********************************************************************
// Support Function Declarations
//
//Teacher's function:

void safegets (char s[], int arraySize);        // gets without buffer overflow
void familyNameDuplicate (char familyName[]);   // marker/tester friendly
void familyNameFound (char familyName[]);       //   functions to print
void familyNameNotFound (char familyName[]);    //     messages to user
void familyNameDeleted (char familyName[]);
void phoneNumberFound (char phoneNumber[]);
void phoneNumberNotFound (char phoneNumber[]);
void printPhoneBookEmpty (void);
void printPhoneBookTitle (void);

//My funcs:

void newContact (char familyName[], char firstName[], char address[], char phoneNumber[], contact **p);//want to modify something
void contactDel (contact **p, char familyName[]);
/* remove head */
contact *contact_search (contact *c, char familyName[]);
/* By Family Name*/
contact *phone_search (contact *c, char phoneNumber[]);
void print_all (contact *head);
void DelAll (contact **p);

//**********************************************************************
// Program-wide Constants
//

const char NULL_CHAR = '\0';
const char NEWLINE = '\n';

//**********************************************************************
// Main Program
//
int main (void)
{
    contact *head=NULL;
    contact *temp=NULL;
    const char bannerString[]
        = "Personal Phone Book Maintenance Program.\n\n";
    const char commandList[]
        = "Commands are I (insert), D (delete), S (search by name),\n"
          "  R (reverse search by phone #), P (print), Q (quit).\n";

    // Declare linked list head.
    //   ADD STATEMENT(S) HERE TO DECLARE LINKED LIST HEAD.

    // announce start of program
    printf("%s",bannerString);
    printf("%s",commandList);

    char response;
    char res[MAX_LENGTH+1];
    char input[MAX_LENGTH+1];
    char familyName[MAX_LENGTH+1];
    char firstName[MAX_LENGTH+1];
    char address[MAX_LENGTH+1];
    char phoneNumber[MAX_LENGTH+1];
        //to pass char arrays to insert function
    do
    {
        printf("\nCommand?: ");
        safegets(input,MAX_LENGTH+1);
        // Response is first char entered by user.
        // Convert to uppercase to simplify later comparisons.
        response = toupper(input[0]);

        if (response == 'I')
        {
        // Insert an phone book entry into the linked list.
            // Maintain the list in alphabetical order by family name.
            //   ADD STATEMENT(S) HERE
        // USE THE FOLLOWING PRINTF STATEMENTS WHEN PROMPTING FOR DATA:
            printf("  family name: ");
        fgets(familyName, MAX_LENGTH+1, stdin);
            printf("  first name: ");
        fgets(firstName, MAX_LENGTH+1, stdin);
            printf("  address: ");
        fgets(address, MAX_LENGTH+1, stdin);
            printf("  phone number: ");
        fgets(familyName, MAX_LENGTH+1, stdin);
        newContact(familyName, firstName, address, phoneNumber, &head);
        }
        else if (response == 'D')
        {
            // Delete an phone book entry from the list.
            //   ADD STATEMENT(S) HERE

            printf("\nEnter family name for entry to delete: ");
        fgets(res,MAX_LENGTH,stdin);
        contactDel(&head, res);

        }
        else if (response == 'S')
        {
            // Search for an phone book entry by family name.

            printf("\nEnter family name to search for: ");
        fgets(familyName, MAX_LENGTH, stdin);
            temp=contact_search(head, familyName);
            if (temp == NULL)
            familyNameFound(res);
            else
        {
            printf("%s\n%s\n%s\n%s\n\n", temp->familyName, temp->firstName, temp->address, temp->phoneNumber);
        }
            //   ADD STATEMENT(S) HERE

        }
        else if (response == 'R')
        {
            // Search for an phone book entry by phone number.
            //ADD STATEMENT(S) HERE
            printf("\nEnter phone number to search for: ");
            fgets(phoneNumber,MAX_LENGTH,stdin);
            temp = phone_search(head, phoneNumber);
            if (temp==NULL)
                phoneNumberNotFound(phoneNumber);
            else
            {
                phoneNumberFound(phoneNumber);
                printf("\n%s\n%s\n%s\n%s\n", temp->familyName, temp->firstName, temp->address, temp->phoneNumber);
            }
        }
        else if (response == 'P')
        {
            // Print the phone book.
            //   ADD STATEMENT(S) HERE
            print_all(head);
        }
        else if (response == 'Q')
        {
            ;// do nothing, we'll catch this below
        }
        else
        {
            // do this if no command matched ...
            printf("\nInvalid command.\n%s\n",commandList);
        }
    } while (response != 'Q');

    // Delete the whole phone book linked list.
    //   ADD STATEMENT(S) HERE
    DelAll(&head);
    // Print the linked list to confirm deletion.
    //   ADD STATEMENT(S) HERE
    print_all (head);
    return 0;
}

//**********************************************************************
// Support Function Definitions

// Function to get a line of input without overflowing target char array.
void safegets (char s[], int arraySize)
{
    int i = 0, maxIndex = arraySize-1;
    char c;
    while (i < maxIndex && (c = getchar()) != NEWLINE)
    {
        s[i] = c;
        i++;
    }
    s[i] = NULL_CHAR;
}

// Function to call when user is trying to insert a family name
// that is already in the book.
void familyNameDuplicate (char familyName[])
{
    printf("\nAn entry for <%s> is already in the phone book!\n"
           "New entry not entered.\n",familyName);
}

// Function to call when a family name was found in the phone book.
void familyNameFound (char familyName[])
{
    printf("\nThe family name <%s> was found in the phone book.\n",
             familyName);
}

// Function to call when a family name was not found in the phone book.
void familyNameNotFound (char familyName[])
{
    printf("\nThe family name <%s> is not in the phone book.\n",
             familyName);
}

// Function to call when a family name that is to be deleted
// was found in the phone book.
void familyNameDeleted (char familyName[])
{
    printf("\nDeleting entry for family name <%s> from the phone book.\n",
             familyName);
}

// Function to call when a phone number was found in the phone book.
void phoneNumberFound (char phoneNumber[])
{
    printf("\nThe phone number <%s> was found in the phone book.\n",
             phoneNumber);
}

// Function to call when a phone number was not found in the phone book.
void phoneNumberNotFound (char phoneNumber[])
{
    printf("\nThe phone number <%s> is not in the phone book.\n",
             phoneNumber);
}

// Function to call when printing an empty phone book.
void printPhoneBookEmpty (void)
{
    printf("\nThe phone book is empty.\n");
}

// Function to call to print title when whole phone book being printed.
void printPhoneBookTitle (void)
{
    printf("\nMy Personal Phone Book: \n");
}

//**********************************************************************
// Add your functions below this line.
//   ADD STATEMENT(S) HERE
void newContact (char familyName[], char firstName[], char address[], char phoneNumber[], contact **head)
{
    contact *testPtr=NULL;
    testPtr = contact_search (*head, familyName);
    if (strcmp(testPtr->familyName, familyName)==0)
    {
        familyNameDuplicate(familyName);
        return;
    }
    else
        testPtr = *head;
    for ( ; strcmp(testPtr->familyName, familyName) < 0; testPtr = testPtr -> link)
    ;
    contact *c = (contact *)malloc (sizeof(contact));//new node
    strcpy(c->familyName, familyName);
    strcpy(c->firstName, firstName);
    strcpy(c->address, address);
    strcpy(c->phoneNumber, phoneNumber);
    if (head==NULL)
    {
        c->link = *head;
        *head=c;
    }
    else
    {
        ;
    }
}

void contactDel (contact **p, char familyName[]) /* remove head */
{
    contact *control=contact_search(*p, familyName);
    if (control != NULL)
    {
        contact *n = control;
        control = control -> link;
        free(n);
    }
}

void DelAll (contact **p)
{
    if (*p != NULL)
    {
        contact *n = *p;
        *p = (*p)->link;
        free(n);
    }
    return;
}

contact *contact_search (contact *c, char familyName[]) /* By Family Name*/
{
    while (c != NULL)
    {
        if (strcmp(c->familyName, familyName)==0)
        {
            return c;
        }
        c = c->link;
    }
    return NULL;
}

contact *phone_search (contact *c, char phoneNumber[])
{
    while (c != NULL)
    {
        if (strcmp(c->phoneNumber, phoneNumber)==0)
        {
            return c;
        }
        c = c->link;
    }
    return NULL;
}

void print_all (contact *head)
{
    if (head == NULL)
    {
        printPhoneBookEmpty();
    }
    else
    {
            printPhoneBookTitle();
        while (head != NULL)
            {
                printf("%s\n%s\n%s\n%s\n\n", head->familyName, head->firstName, head->address, head->phoneNumber);
            head = head->link;
            }
    }
}

程序应该将输入保存在列表中，然后在从用户获得选项后打印它们。等等，但为什么我得到分割失败？

最佳答案

除了上面的testPtr是NULL之外，您还将遇到以下问题：

for ( ; strcmp(testPtr->familyName, familyName) < 0; testPtr = testPtr -> link)
    ;

如果testPtr为空，则不能调用strcmp(testPtr->familyName，也不能调用testPtr = testPtr -> link。（这是插入时的最后一个SegFault）
（注意：如果您使用一组空大括号（例如;）而不是尾随的for (...) {}，则更容易阅读）
但是，当您Search (S)时，您将永远不会匹配testPtr->familyName，因为在使用fgets阅读之后，您的familyName包含：

+---+---+---+---+---+---+---+---+---+
| S | o | m | e | n | a | m | e | \n|  <== note trailing '\n' included
+---+---+---+---+---+---+---+---+---+

要修剪后面的换行符，请使用：

        if (!fgets(familyName, MAX_LENGTH, stdin)) {
            fprintf (stderr, "error: user canceled input.\n");
            continue;
        }
        size_t len = strlen (familyName);        /* get length */
        if (len && familyName[len - 1] == '\n')  /* check last char '\n' */
            familyName[--len] = 0;               /* overwrite with nul-char */
        else {
            /* handle line too long */
        }

您需要在每次使用fgets时修剪后面的换行符，并且还应该处理“行太长”的情况。您也可以使用任何其他字符串函数来定位尾随的'\n'，例如char *nl = strchr (familyName, '\n'); if (nl) *nl = 0;，等等。。创建一个简短的函数来处理这个杂务将节省大量的代码重复。
即使进行了这些更改，您的Search (S)仍然会报告一个空列表——但您的SegFault已被修复。解决那个问题就交给你了。
另外，在你分配

contact *c = (contact *)malloc (sizeof(contact));//new node

您必须验证(c != NULL)因为malloc可能会失败，或者您可以耗尽可用内存（这越来越可能为10*2中的每个字符串分配contact字节）。另请参见：Do I cast the result of malloc?
要调节内存使用，应该为familyName、firstName、address和phoneNumber分配内存。strdup提供了一种简单的执行方式。只需将contacts中的每个字符串声明为指针，然后在读取（例如familyName和fgets并修剪换行符）之后，只需允许strdup分配所需的确切空间并将familyName复制到新的内存块。那就很简单了

c->familyName = strdup (familyName);

由于strdup分配，您还应该验证它是否成功，例如。

if (!c->familyName) {
    /* handle error */
}

如果你遇到任何其他障碍你都无法克服，请告诉我，我很乐意进一步帮助你。