Segfault在C中重新分配

Question

雖然使用倍增策略第二次調整重新分配的大小，但我卻遇到了段錯誤。

code : 

stack.c :

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<assert.h>
#include "stack.h"

/* Allocate the fields inside the stack */
void stackNew(my_stack* s){
        s->alloc_length = STACKSIZE;
        s->logical_length = 0;
        s->elems = malloc(STACKSIZE * sizeof(int)); // creates 4 int boxes to store the ints
        assert(s->elems != NULL);
}

/* Free the Heap memory, if allocated any */
void stackDispose(my_stack* s){
        free(s->elems);
}

/* Push new elements into the stack */
void stackPush(my_stack* s,int data){
        if(s->alloc_length <= s->logical_length){ // If the alloclength and the logicallength are the same, then we may need to resize it
                s->alloc_length *= 2;   // Doubling stratgie
                printf("\n Reallocated : size : %d \n",s->alloc_length);
                s->elems = realloc(s->elems,s->alloc_length);
                assert(s->elems != NULL);
        }
        printf("alloc : %d logical : %d \n",s->alloc_length,s->logical_length);
        s->elems[s->logical_length] = data;
        s->logical_length++;
}

/* Pop the elements out of the stack */
int stackPop(my_stack* s){
        s->logical_length--;
        if(s->logical_length <= 0){
                printf("\n cannot pop!! stack is empty!! \n");
                return 2;
        }
        return s->elems[s->logical_length];
}

void stackDisplay(my_stack* s){
        int i = 0;
        for(i = 0; i < s->logical_length; i++){
                printf("\n s->elems : %d \n",(s->elems[i]));
        }
}

/* Main */
int main(){
        my_stack stack;
        int pop;
        printf("\n Begin!! \n");
        stackNew(&stack);
        stackPush(&stack,10);
        stackPush(&stack,20);
        stackPush(&stack,30);
        stackPush(&stack,40);
        stackPush(&stack,50);
        stackPush(&stack,60);
        stackPush(&stack,70);
        stackPush(&stack,80);
        stackPush(&stack,90);
        stackPush(&stack,100);
        stackDisplay(&stack);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        pop = stackPop(&stack);
        printf("\n Popping!! - %d \n",pop);
        stackDisplay(&stack);
        stackDispose(&stack);
        printf("\n End!! \n");
        return 0;
}


stack.h : 

typedef struct __my_stack{
        int* elems;
        int logical_length;
        int alloc_length;
}my_stack;

#define STACKSIZE 4

void stackNew(my_stack* s);
void stackDispose(my_stack* s);
void stackPush(my_stack* s,int data);
int stackPop(my_stack* s);

output : 

root@ab# ./a.out

 Begin!!
alloc : 4 logical : 0
alloc : 4 logical : 1
alloc : 4 logical : 2
alloc : 4 logical : 3

 Reallocated : size : 8
alloc : 8 logical : 4
alloc : 8 logical : 5
alloc : 8 logical : 6
alloc : 8 logical : 7

 Reallocated : size : 16
*** Error in `./a.out': realloc(): invalid next size: 0x0000000000986010 ***
Aborted (core dumped)

Answer 1

在重新分配中，您未能包含

* sizeof(int)

部分，因此您沒有重新分配足夠的內存。

Answer 2

您忘記在realloc（）中乘以sizeof（int）