realloc（）在c ..打印垃圾值

Question

我已经上传了所有的代码..这是工作正在进行..请检查realloc（），因为如果我没有达到realloc（）的条件一切工作正常。 ..Thanks evry1 ..

// contactinfo.h-- header file 
    #ifndef _ELEMENT_H 

    #define _ELEMENT_H 

    typedef struct ContactInfo ContactInfo; 

    struct ContactInfo{ 
    char Name[30]; 

    char email_id[50]; 

    int phon_num; 

    }; 


typedef ContactInfo **ContactList; 

#endif 

//contactops.h 

    #include "contactInfo.h" 

ContactList createCL(int size); 

void addContact(ContactList clist1, ContactList clist2, ContactInfo ci, int size); 

ContactInfo *findByName(ContactList cl, char *name); 

ContactInfo *findByNumber(ContactList cl, int num); 

void deleteContactByName(ContactList cl, ContactList c2, char *name); 

void deleteContactByNumber(ContactList cl, ContactList c2, int num); 

void printContacts(ContactList cl); 

void Merge_Sort(int hi, int mid, int lo, ContactList c); 

void Merge(int hi , int lo, ContactList c); 

//contactopsarr.c 的#include

#include <string.h> 

#include <stdlib.h> 

#include "contactInfo.h" 

#include "contactOps.h" 


int counter =0;      

int buff_size = 5;     //pre defined Size 

ContactList arr_name;    //to hold the pointers to the locations of 
the shared data by name 

ContactList arr_num;    //to hold the pointers to the locations of the shared data by number 

ContactInfo *list ;     // to hold the shared date 

int main(){ 

    char search_name[20];   //buffer to hold the name to be searched 

    int search_numb;    //buffer to hold the number to be searched 
    arr_num = createCL(buff_size); 

    arr_name = createCL(buff_size); 

    /************************* Allocation Of the Shared Data *******************************/ 

    list = malloc(buff_size * sizeof(ContactInfo)); 

    if(list == NULL){ 
     printf("Memmory Allocation Of the shared Data failed..\n"); 
    } 

    /************************ Allocation Completed *****************************************/ 


    char choice;     //to hold "y" or "n" 

    printf("Do you want to Continue..."); 

    scanf(" %c",&choice); 

    int option;      //to hold Choice number to be selected 
    ContactInfo ci;     //buffer to hold the information to be added 

    while(choice == 'Y'|| choice=='y') 
    { 
     printf("\n1.Add Contact\n2.FIND Contact by NAME\n3.FIND Contact by NUMBER\n4.DELETE contact by NAME\n5.DELETE contact by NUMBER\n6.PRINT contact\n"); 
     printf("Enter Your Option..\n"); 
     scanf(" %d",&option); 
     switch(option) 
     { 
      case 1: printf("Enter the Name:\n"); 
        scanf(" %s",&ci.Name); 
        printf("Enter the Number:\n"); 
        scanf(" %d",&ci.phon_num); 
        printf("Enter the Email-id:\n"); 
        scanf(" %s",&ci.email_id); 
        addContact(arr_num , arr_name, ci, buff_size); 
        break; 

     /* case 2: printf("Enter the name to be Searched..\n"); 
        scanf(" %s",&search_name); 
        findByName(list, search_name); 
        break; 

      case 3: printf("Enter the number to be Searched..\n"); 
        scanf(" %s",&search_numb); 
        findByNumber(list,search_numb); 
        break; 

      case 4: break; 

      case 5: break; 
*/ 
      case 6: printContacts(arr_num); 
        break; 

      default : printf("Enter a Correct Choice...\n"); 

     } 

    } 

} 



ContactList createCL(int size){ 
    ContactList temp = malloc(buff_size * sizeof(ContactInfo *)); 
    return temp; 
} 

void addContact(ContactList clist1, ContactList clist2, ContactInfo ci, int size) 
{ 

    printf("Val of counter : %d\n",counter); 
    printf("Val of buff_size : %d\n", size); 
    if((counter+1)>=size) 
    { 
     /*realloc(list, (buff_size +5)*sizeof(ContactInfo)); 
     //ContactInfo *temp = malloc((size+5)*sizeof(ContactInfo)); 
     if(list == NULL){ 
      printf("Extended Memory Allocation(0) Failed..Quiting.."); 
      exit(1); 
     } 
     /*memcpy(temp, list, counter-1); 
     list = temp; 
     free(temp);*/ 
     ContactInfo *tmp_list = realloc(list, (buff_size + 5) * sizeof(ContactInfo)); 
     if (tmp_list == NULL) 
     { 
      free(list); 
      printf("Extended Memory Allocation(0) Failed..Quiting.."); 
      exit(1); 
     } 
     list = tmp_list; 



     /*realloc(clist1, (size +5)*sizeof(ContactInfo*)); 
     //ContactList temp1 = malloc((size+5)*sizeof(ContactList)); 
     if(clist1 == NULL){ 
      printf("Extended Memory Allocation(1) Failed..Quiting.."); 
      exit(1); 
     } 
     /*memcpy(temp1, clist1, counter-1); 
     clist1 = temp1;*/ 
     ContactList tmp_list1 = realloc(clist1, (buff_size + 5) * sizeof(ContactInfo *)); 
     if (tmp_list1 == NULL) 
     { 
      free(clist1); 
      printf("Extended Memory Allocation(1) Failed..Quiting.."); 
      exit(1); 
     } 
     clist1 = tmp_list1; 


     /*realloc(clist1, (size +5)*sizeof(ContactInfo*)); 
     //ContactList temp2 = malloc((size+5)*sizeof(ContactList)); 
     if(clist2 == NULL){ 
      printf("Extended Memory Allocation(2) Failed..Quiting.."); 
      exit(1); 
     } 
     /*memcpy(temp2, clist2, counter-1); 
     clist2 = temp2; 
     */ 
     ContactList tmp_list2 = realloc(clist2, (buff_size + 5) * sizeof(ContactInfo *)); 
     if (tmp_list2 == NULL) 
     { 
      free(clist2); 
      printf("Extended Memory Allocation(2) Failed..Quiting.."); 
      exit(1); 
     } 
     clist2 = tmp_list2; 

     buff_size = buff_size + 5; 
    } 

    list[counter] = ci; 
    clist1[counter] = &list[counter];    //holding the location of the list[counter].. 
    clist2[counter] = &list[counter]; 

    counter = counter + 1;    //updating the counter 
} 



ContactInfo *findByName(ContactList cl, char *name) 
{ 

} 

ContactInfo *findByNumber(ContactList cl, int num) 
{ 


} 


/* 
void deleteContactByName(ContactList cl, ContactList c2, char *name); 
void deleteContactByNumber(ContactList cl, ContactList c2, int num);*/ 

void printContacts(ContactList cl) 
{ 
    int i ; 
    for(i=0 ; i<20; i++) 
    { 
     printf(" %s\n", cl[i]->Name); 
    } 
} 

void Merge(int hi , int lo, ContactList c) 
{ 
    if(hi>lo) 
    { 
     int mid = (hi + lo)/2; 
     Merge(mid, lo, c); 
     Merge(mid+1, hi, c); 
     Merge_Sort(hi, mid, lo, c); 

    } 
} 

void Merge_Sort(int hi, int mid, int lo, ContactList c) 
{ 
    ContactList arr1 = malloc(((counter/2)+1)*sizeof(ContactInfo *)); 
    if(arr1 == NULL) 
    { 
     printf("Memory Allocation(3) failed"); 
    } 

    ContactList arr2 = malloc(((counter/2)+1)*sizeof(ContactInfo *)); 
    if(arr2 == NULL) 
    { 
     printf("Memory Allocation(4) failed"); 
    } 

    int i, j; 
    int limit_first = mid - lo + 1 ; 
    int limit_second = hi - mid; 

    for(i=0; i<limit_first; i++) 
    { 
     arr1[i] = c[i]; 
    } 

    for(j=0; j<limit_second; i++) 
    { 
     arr2[j] = c[mid + j + 1]; 
    } 

    /*ContactInfo temp; 
    strcpy(temp.Name , "zzzzzzz"); 
    temp.phon_num = 99999999999; 
    strcpy(temp.email_id, "zzzzzzz"); 

    arr1[i] = &temp; 
    arr1[j] = &temp;*/ 

    int k; 
    i=0; 
    j=0; 
    for(k=0; k<hi; k++) 
    { 

     if(arr1[i] >= arr2[j]) 
     { 
      c[k] = arr2[j]; 
      j++; 
     } 

     else 
     { 
      c[k] = arr1[i]; 
      i++; 
     } 
    } 

} 

Answer 1

我发现错误......我并不需要通过（BUFF_SIZE + 5）*的sizeof（CONTACTINFO *），而只是realloc的（列表，BUFF_SIZE + 5）; ...工作对我来说..

Answer 2

一个问题是：realloc()返回地址的新分配的内存的：店的返回值realloc()。它可能会分配一个全新的内存块，并将被重新分配的内存的内容复制到以前的内存中。访问先前的内存，现在为free() d，是未定义的行为，并且是重新分配后垃圾输出的可能原因。

realloc()的返回值保存到临时指针和更新list（并与realloc()结合使用的其它指针）仅如果返回非NULL指针：

ContactInfo* tmp_list = realloc(list, (buff_size + 5) * sizeof(ContactInfo)); 
if (tmp_list == NULL) 
{ 
    free(list); 
    fprintf(stderr, "Extended Memory Allocation(0) Failed..Quiting.."); 
    exit(1); 
} 
list = tmp_list; 

Answer 3

我假定ContactList是一个typedef结构指针？

当您将clist1传递给此函数时，它将包含一个指向内存块的指针。

realloc 可能将此指针更改为其他内容（并将所有内存内容移至此新指针）。

当您在传递clist1作为指针时退出此函数时，此新值将丢失。

为了确保此功能正常工作，您需要将指针传递给指针，并在函数中对其进行取消引用。这确保指针是否改变，调用函数会知道它。

void addContact(ContactList* clist1, ContactList clist2, ContactInfo ci, int size) 
{