堆栈实现崩溃时，试图打印堆栈的元素

Question

我想实现一个使用数组的动态堆栈。用户输入他想要放入堆栈的单词的字母数。如果堆栈为空，则会创建一个块来保存用户传递到堆栈的信息。如果没有，那么堆栈被重新分配，以便它可以保存更多的信息块（单词）。然后用户输入他想要放入堆栈的单词（在打印堆栈索引的那一部分）。在第二个词完成进入堆栈后，程序似乎崩溃。

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

typedef struct stackElement { 
    int stringLength; 
    char *name; 
} StackElement; 
int Push(StackElement **stack,int *index); 

int main() 
{ 
    StackElement *stack = NULL; 
    int index = -1; 
    Push(&stack,&index); 
    printf("The index is : %d\n", index); 
    printf("The top word of the stack is %s\n", stack[index].name); 
    Push(&stack,&index); 
    printf("The index is : %d\n", index);//Crashes after this command is executed 
    printf("The second word of the stack is %s\n", stack[index].name); 
    system("PAUSE"); 
    return 0; 
} 

int Push(StackElement **stack,int *index) 
{ 
    if (*stack == NULL) { 
     printf("The stack is empty\n"); 
     *index = *index + 1 ; 
     *stack = malloc(sizeof(StackElement)); 
    } else { 
     printf("The stack is not empty\n"); 
     *index = *index + 1 ; 
     //Adding enough space for one more element in the stack 
     *stack = realloc(*stack,sizeof(StackElement)*(*index+1)); 
    } 
    printf("Enter the length of the word you want in the stack\n"); 
    scanf("%d", &(*stack[*index]).stringLength); 
    (*stack[*index]).name = malloc(sizeof(char)*(*stack[*index]).stringLength); 
    printf("Enter the word in the stack\n"); 
    scanf("%s", (*stack[*index]).name); 
    return 0; 
} 

Answer 1

您的代码是不容易的，因为有很多的指针读取，但据我了解，你滥用realloc()。

当第一次分配堆栈时，可以使用*stack = malloc(sizeof(StackElement))这很好。

当您重新分配堆栈（realloc(*stack,sizeof(StackElement)*(*index))）时，您将size作为结构体的维数乘以变量index;在此时程序索引等于1，因此您分配的内存大小与之前（sizeof(StackElement)）完全相同，然后访问索引大于0的内存，则会出现分段错误。

Answer 2

这不是很好，但至少它工作！你应该从你的函数中删除你的分配。

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


typedef struct stackElement 
{ 
    int stringLength; 
    char *name; 

} StackElement; 

int Push(StackElement **stack,int *index); 



int main() 
{ 
    StackElement *stack = NULL; 
    int index = -1; 

     if(stack == NULL) 
    { 
     printf("The stack is empty\n"); 
     index = index + 1 ; 
     stack = (StackElement*)malloc(sizeof(StackElement)); 
    } 
    else 
    { 
     printf("The stack is not empty\n"); 
     index = index + 1 ; 
     stack = realloc(stack,sizeof(StackElement)*(index+1));//Adding enough space for one more element in the stack 
    } 

    Push(stack,&index); 

    printf("The index is : %d\n", index); 

    printf("The top word of the stack is %s\n", stack[index].name); 

      if(stack == NULL) 
    { 
     printf("The stack is empty\n"); 
     index = index + 1 ; 
     stack = (StackElement*)malloc(sizeof(StackElement)); 
    } 
    else 
    { 
     printf("The stack is not empty\n"); 
     index = index + 1 ; 
     stack = realloc(stack,sizeof(StackElement)*(index+1));//Adding enough space for one more element in the stack 
    } 


    Push(stack,&index); 

    printf("The index is : %d\n", index);//Crashes after this command is executed 

    printf("The second word of the stack is %s\n", stack[index].name); 

    system("PAUSE"); 

    return 0; 
} 



int Push(StackElement *stack,int *index) 
{ 



    printf("Enter the length of the word you want in the stack\n"); 

    scanf("%d", &(stack[*index]).stringLength); 

    (stack[*index]).name = malloc(sizeof(char)*(stack[*index]).stringLength); 

    printf("Enter the word in the stack\n"); 

    scanf("%s", (stack[*index]).name); 




    return 0; 

}