其实解决问题的方法很简单

news2025/1/25 9:22:30

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本例是一个动态数组的例子，实现数据的增加、删除、根据索引修改数值、获取数值。

dynamic_array.c

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

dynamic_array_t *init_dynamic_array()
{
    dynamic_array_t *da = malloc(sizeof(dynamic_array_t));
    da->items = calloc(DEFAULT_CAPACITY, sizeof(void *));
    da->capacity = DEFAULT_CAPACITY;

    return da;
}

void *add(dynamic_array_t *da, const void *value)
{
    if (da->size >= da->capacity)
    {
        void **newItems = realloc(da->items, (da->capacity <<= 1) * sizeof(void **));
        //free(da->items);

        da->items = newItems;
    }

    void *copy_value = retrive_copy_of_value(value);
    da->items[da->size++] = copy_value;

    return copy_value;
}

void *put(dynamic_array_t *da, const void *value, const unsigned index)
{
    if (!contains(da->size, index))
        return INDEX_OUT_OF_BOUNDS;

    free(da->items[index]);
    void *copy_value = retrive_copy_of_value(value);
    da->items[index] = copy_value;

    return copy_value;
}

void *get(dynamic_array_t *da, const unsigned index)
{
    if (!contains(da->size, index))
        return INDEX_OUT_OF_BOUNDS;

    return da->items[index];
}

void delete (dynamic_array_t *da, const unsigned index)
{
    if (!contains(da->size, index))
        return;

    for (unsigned i = index; i < da->size; i++)
    {
        da->items[i] = da->items[i + 1];
    }

    da->size--;

    free(da->items[da->size]);
}

unsigned contains(const unsigned size, const unsigned index)
{
    //printf("size:%d,index:%d\n", size, index);
    if (size >= 0 && index < size)
        return 1;

    printf("index [%d] out of bounds!\n", index);
    return 0;
}

void *retrive_copy_of_value(const void *value)
{
    void *value_copy = malloc(sizeof(void *));
    memcpy(value_copy, value, sizeof(void *));

    return value_copy;
}

dynamic_array.h

#ifndef __DYNAMIC_ARRAY__
#define __DYNAMIC_ARRAY__
#define DEFAULT_CAPACITY 1 << 4
#define INDEX_OUT_OF_BOUNDS NULL

typedef struct dynamic_array
{
    void **items;
    unsigned size;
    unsigned capacity;
} dynamic_array_t;

extern dynamic_array_t *init_dynamic_array();

extern void *add(dynamic_array_t *da, const void *value);

extern void *put(dynamic_array_t *da, const void *value, unsigned index);

extern void *get(dynamic_array_t *da, const unsigned index);

extern void delete (dynamic_array_t *da, const unsigned index);

unsigned contains(const unsigned size, const unsigned index);

extern void *retrive_copy_of_value(const void *value);

main.c

#include "dynamic_array.h"

int main()
{
    dynamic_array_t *da = init_dynamic_array();

    for (int i = 1; i <= 50; i++)
    {
        add(da, &i);
    }
    
    
    delete (da, 10);
    int value = 999;
    put(da, &value, 0);

    #if 1
    //value = 666;

    int another_value = 666;

    add(da, &another_value);
    #endif

#if 0
    for (int i = 0; i < da->size; i++)
    {
        printf("value[%d]=%d\n",i, *(int *)get(da, i));
    }
#endif

    int value_for_invalid_index = 10000;

    //put(da, &value_for_invalid_index, 150);
    //put(da, &value_for_invalid_index, 65);
    put(da, &value_for_invalid_index, 49);

    for (int i = 0; i < da->size; i++)
    {
        printf("value[%d]=%d\n",i, *(int *)get(da, i));
    }

    free(da->items);
    return 0;
}

Makefile:

CC = gcc
CFLAGS = -g -Wall

all: main

main: main.o dynamic_array.o
	$(CC) $(CFLAGS) $^ -o $@

dynamic_array.o: dynamic_array.c
	$(CC) $(CFLAGS) -c $^

clean: 
	rm *.o main

刚开始运行结果是这样的：

于是乎这样调试：

利用core文件调试：

先设置一下

ulimit -c unlimited

运行一下在当前目录下生成core文件

root@ubuntu-virtual-machine:/home/ubuntu/test# gdb main

gdb结合core文件调试

代码修正后运行结果：

value[0]=999
value[1]=2
value[2]=3
value[3]=4
value[4]=5
value[5]=6
value[6]=7
value[7]=8
value[8]=9
value[9]=10
value[10]=12
value[11]=13
value[12]=14
value[13]=15
value[14]=16
value[15]=17
value[16]=18
value[17]=19
value[18]=20
value[19]=21
value[20]=22
value[21]=23
value[22]=24
value[23]=25
value[24]=26
value[25]=27
value[26]=28
value[27]=29
value[28]=30
value[29]=31
value[30]=32
value[31]=33
value[32]=34
value[33]=35
value[34]=36
value[35]=37
value[36]=38
value[37]=39
value[38]=40
value[39]=41
value[40]=42
value[41]=43
value[42]=44
value[43]=45
value[44]=46
value[45]=47
value[46]=48
value[47]=49
value[48]=50
value[49]=10000