Question

在下面的程序中，即使我将垃圾值获取到结构成员之一，我仍在正确分配用于指针的内存，然后正确分配各个指针并设置值。我不知道我到底要去哪里。

下面程序的示例输出是：

***CK: H2 nSupport: 0

CK: H2 nSupport: 1303643608
CK: FR2 nSupport: 0

CK: H2 nSupport: 1303643608
CK: FR2 nSupport: 0
***CK: SP2 nSupport: 0

尽管开始时设置正确，但我不知道如何获得值1303643608。

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

#define NOK 15
#define ML 100

typedef struct sample_test_for_ties_t
{
    char sender[NOK];
    char receiver[NOK];
    char message[ML];
}sample_test_for_ties;

typedef struct CUOfS_t{
    char cK[NOK];
    char eK[NOK];
    char nK[NOK];
    char AL[ML];
    int nSupport;
}CUOfS;

CUOfS **Btenders = NULL;
sample_test_for_ties test_ties[] = {
                                    {"H2","ICY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                    {"FR2","AIY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                    {"SP2","LAY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                    {"H30","ICY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                    {"F30","AIY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                    {"W30","LAY", "fmaabghijklmmcdenoopqrstuvwxyz"},
                                   };

void InitBtenders(int numOfBCtenders)
{
    int count =0;
    if(!Btenders) 
    {
        if(Btenders = (CUOfS **)malloc(sizeof (**Btenders) * numOfBCtenders))
        {
            while(count < numOfBCtenders)
            {
                Btenders[count] = NULL;
                count++;
            }
        }
        else
        {
            printf("Malloc failed\n");
        }
    }
}

void freeBtenders(int numOfBCtenders)
{
    int count =0;
    if(Btenders)
    {
        while(count<numOfBCtenders)
       {
             if(Btenders[count]) {
                    free(Btenders[count]);
                    Btenders[count] = NULL;
             }
             count++;
       }
        free(Btenders);
        Btenders = NULL;
    }
}

void UpdateBtendersInfo(char *aContenders)
{
    static int counter =0;
    if(Btenders)
    {
        if(Btenders[counter] == NULL) {
            Btenders[counter] = (CUOfS *)malloc(sizeof (Btenders[counter]));
            if(Btenders[counter])
            {
                strcpy(Btenders[counter]->cK,aContenders);
                strcpy(Btenders[counter]->eK,"\0");
                strcpy(Btenders[counter]->nK,"\0");
                memset(Btenders[counter]->AL,0,sizeof(Btenders[counter]->AL));
                Btenders[counter]->nSupport = 0;
                counter++;
            }
            else
            {
                printf("Insufficient memory for Btender\n");
            }
       }
    }
    else
    {
        printf("Looks like memory not allocated for Btenders\n");
    }
    int count =0;
    while(count <counter && Btenders[count])
    {
        printf("***CK: %s nSupport: %d\n",Btenders[count]->cK,Btenders[count]->nSupport);
        count++;
    }
    printf("\n");
}

int main()
{
    int numOfBCtenders = 3;
    int noc =0;
    InitBtenders(numOfBCtenders);
    while(noc < numOfBCtenders)
    {
        UpdateBtendersInfo(test_ties[noc].sender);
        noc++;
    }
    freeBtenders(numOfBCtenders);
    return 0;
}

我希望

***CK: H2 nSupport: 0

但是我得到了

***CK: H2 nSupport: 1303643608

Answer 1

为Btenders分配内存的方式不正确。

Btenders = (CUOfS **)malloc(sizeof (**Btenders) * numOfBCtenders)   // WRONG

sizeof (**Btenders)与sizeof(CUOfS)相同，但是您需要sizeof(CUOfS*)：

Btenders = (CUOfS **)malloc(sizeof (*Btenders) * numOfBCtenders)    // FIXED

类似地：

Btenders[counter] = (CUOfS *)malloc(sizeof (Btenders[counter]));    // WRONG

sizeof (Btenders[counter])与sizeof(CUOfS*)相同，但是您需要sizeof(CUOfS)：

Btenders[counter] = (CUOfS *)malloc(sizeof (*(Btenders[counter]))); // FIXED

即使正确初始化，C结构也会打印错误的值

1 个答案: