c - 释放结构数组的元素？

Question

该程序用于创建项目库存、查看库存并允许用户通过项目编号删除项目。一切都通过一个结构数组，在删除库存项目后，我很难释放数组元素，方法是通过一个函数将其上方的所有其他内容移动到数组中。任何帮助表示赞赏。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_INVENTORY_SIZE 100

typedef struct {
    char item_Number[4];
    char item_Name[20];
    float item_Profit;
    float latest_Price;
    float selling_Price;
    unsigned int stock;
    unsigned int total_Sold;
}InventoryItemType;

void MainMenu();
void displayInventory(InventoryItemType *, int);
void displaySales(InventoryItemType *, int);
InventoryItemType *addItem(void);
InventoryItemType deleteItem(InventoryItemType *, int);

int main()
{
    int i=0, item_count=0;
    char selection, code[4];
    InventoryItemType inventoryItems[MAX_INVENTORY_SIZE];
    while(1)
    {
        MainMenu();

        scanf(" %c", &selection);
        switch(selection) 
        {
        case 'A' :
            displayInventory(inventoryItems, item_count);
            system("pause");
            system("cls");
            continue;
        case 'B' :
            displaySales(inventoryItems, item_count);
            system("pause");
            system("cls");
            continue;
        case 'C' :
            if(item_count == MAX_INVENTORY_SIZE - 1)
            {
                printf("Array is full\n");
                system("pause");
                continue;
            }
            inventoryItems[item_count] = *addItem();
            item_count++;
            continue;
        case 'D' :
            *inventoryItems=deleteItem(inventoryItems, item_count);
            free(&inventoryItems[item_count]);
            item_count--;
            continue;
        case 'E' :
        case 'F' :
        case 'G' :
        case 'H' :
        default :
            printf("Invalid Entry\n" );
            system("pause");
        }
        system("cls");
    }
}
void MainMenu()
{
    printf("A. Display Inventory\n");
    printf("B. Display Sales\n");
    printf("C. Add Item\n");
    printf("D. Remove Item\n");
    printf("E. Enter Shipment\n");
    printf("F. Update Sales\n");
    printf("G. Sort\n");
    printf("H. Exit\n");
    printf("Make a selection\n");
}
void displayInventory(InventoryItemType *display, int key)
{
    system("cls");
    {
        int i;
        for(i=0; i<key; i++)
        {
            printf("Item No.:%s\n", display[i].item_Number);
            printf("Item Name:%s\n", display[i].item_Name);
            printf("Item Stock:%d\n",display[i].stock);
            printf("Item Purchased Price:%.2f\n", display[i].latest_Price);
            printf("Total Value of Items:%.2f\n", (display[i].stock)*(display[i].latest_Price));
            printf("\n");
        }
    }
}
void displaySales(InventoryItemType *display, int key)
{

    int i;
    float total_profit=0;
    system("cls");
    for(i=0; i<key; i++)
    {
        printf("Item No.:%s\n", display[i].item_Number);
        printf("Item Name:%s\n", display[i].item_Name);
        printf("Number of Item Sold:%d\n", display[i].total_Sold);
        printf("Item Selling Price:%.2f\n", display[i].selling_Price);
        printf("Total Profit from Item:%.2f\n", (display[i].selling_Price-display[i].latest_Price)*display[i].total_Sold);
        total_profit=total_profit+((display[i].selling_Price-display[i].latest_Price)*display[i].total_Sold);
        if(i==key-1)
        printf("\nTotal Over-all Profit:%.2f", total_profit);
        printf("\n\n");
    }
}
InventoryItemType *addItem(void)
{
    InventoryItemType *current = (InventoryItemType*) malloc (sizeof *current);
    system("cls");
    if(current == NULL)
        return NULL;
    printf("\nEnter details of item \n\n");
    printf("Enter Item no: \n");
    scanf("%s", current->item_Number);
    printf("Enter Item Name: \n");
    scanf("%s", current->item_Name);
    printf("Enter Stock: \n");
    scanf("%d", &current->stock);
    printf("Enter Purchase Price: \n");
    scanf("%f", &current->latest_Price);
    current->selling_Price=(current->latest_Price)*1.5;
    current->total_Sold=0;
    system("cls");
    return current;
}
InventoryItemType deleteItem (InventoryItemType *deleted, int item_count)
{
    char code[4];
    int i;
    printf("Enter Item Number to be Deleted\n");
    scanf("%3s", code);
    for(i=0;i<item_count;i++)
    {
        if(strcmp(code,deleted[i].item_Number)==0)
                break;
    }
    for(;i<item_count; i++)
        deleted[i]=deleted[i+1];
    return *deleted;
}  

在@Barmar 的帮助下进行编辑:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_INVENTORY_SIZE 100

typedef struct {
    char item_Number[4];
    char item_Name[20];
    float item_Profit;
    float latest_Price;
    float selling_Price;
    unsigned int stock;
    unsigned int total_Sold;
}InventoryItemType;
void MainMenu();
void displayInventory(InventoryItemType *[], int);
void displaySales(InventoryItemType *[], int);
InventoryItemType *addItem(void);
InventoryItemType deleteItem(InventoryItemType *, int);

int main()
{
    int i=0, item_count=0;
    char selection, code[4];
    InventoryItemType *inventoryItems[MAX_INVENTORY_SIZE];
    while(1)
    {
        MainMenu();

        scanf(" %c", &selection);
        switch(selection) 
        {
        case 'A' :
            displayInventory(inventoryItems, item_count);
            system("pause");
            system("cls");
            continue;
        case 'B' :
            displaySales(inventoryItems, item_count);
            system("pause");
            system("cls");
            continue;
        case 'C' :
            if(item_count == MAX_INVENTORY_SIZE - 1)
            {
                printf("Array is full\n");
                system("pause");
                continue;
            }
            inventoryItems[item_count] = addItem();
            item_count++;
            continue;
        case 'D' :
            **inventoryItems=deleteItem(*inventoryItems, item_count);
            item_count--;
            continue;
        case 'E' :
        case 'F' :
        case 'G' :
        case 'H' :
        default :
            printf("Invalid Entry\n" );
            system("pause");
        }
        system("cls");
    }
}
void MainMenu()
{
    printf("A. Display Inventory\n");
    printf("B. Display Sales\n");
    printf("C. Add Item\n");
    printf("D. Remove Item\n");
    printf("E. Enter Shipment\n");
    printf("F. Update Sales\n");
    printf("G. Sort\n");
    printf("H. Exit\n");
    printf("Make a selection\n");
}
void displayInventory(InventoryItemType *display[], int key)
{
    system("cls");
    {
        int i;
        for(i=0; i<key; i++)
        {
            printf("Item No.:%s\n", display[i]->item_Number);
            printf("Item Name:%s\n", display[i]->item_Name);
            printf("Item Stock:%d\n",display[i]->stock);
            printf("Item Purchased Price:%.2f\n", display[i]->latest_Price);
            printf("Total Value of Items:%.2f\n", (display[i]->stock)*(display[i]->latest_Price));
            printf("\n");
        }
    }
}
void displaySales(InventoryItemType *display[], int key)
{

    int i;
    float total_profit=0;
    system("cls");
    for(i=0; i<key; i++)
    {
        printf("Item No.:%s\n", display[i]->item_Number);
        printf("Item Name:%s\n", display[i]->item_Name);
        printf("Number of Item Sold:%d\n", display[i]->total_Sold);
        printf("Item Selling Price:%.2f\n", display[i]->selling_Price);
        printf("Total Profit from Item:%.2f\n", (display[i]->selling_Price-display[i]->latest_Price)*display[i]->total_Sold);
        total_profit=total_profit+((display[i]->selling_Price-display[i]->latest_Price)*display[i]->total_Sold);
        if(i==key-1)
        printf("\nTotal Over-all Profit:%.2f", total_profit);
        printf("\n\n");
    }
}
InventoryItemType *addItem(void)
{
    InventoryItemType *current = (InventoryItemType*) malloc (sizeof *current);
    system("cls");
    if(current == NULL)
        return NULL;
    printf("\nEnter details of item \n\n");
    printf("Enter Item no: \n");
    scanf("%s", current->item_Number);
    printf("Enter Item Name: \n");
    scanf("%s", current->item_Name);
    printf("Enter Stock: \n");
    scanf("%d", &current->stock);
    printf("Enter Purchase Price: \n");
    scanf("%f", &current->latest_Price);
    current->selling_Price=(current->latest_Price)*1.5;
    current->total_Sold=0;
    system("cls");
    return current;
}
InventoryItemType deleteItem (InventoryItemType *deleted, int item_count)
{
    char code[4];
    int i;
    printf("Enter Item Number to be Deleted\n");
    scanf("%3s", code);
    for(i=0;i<item_count;i++)
    {
        if(strcmp(code,deleted[i].item_Number)==0)
                break;
    }
    free(deleted[i]);
    for(;i<item_count; i++)
        deleted[i]=deleted[i+1];
    return *deleted;
}

Answer 1

inventoryItems 的元素不是动态分配的，因此您无法释放它们。它们直接包含在数组中。当你这样做时:

inventoryItems[item_count] = *add_item();

您正在取消引用指针，而不是将指针存储在数组中。这会复制动态分配的结构，并丢弃其指针(因此会发生内存泄漏)。

您应该更改此数组的类型以包含指针:

InventoryItemType * inventoryItems[MAX_INVENTORY_SIZE];

那么你不应该解引用 addItem 返回的指针，你应该直接分配它:

inventoryItems[item_count] = add_item();

然后你释放它:

free(inventoryItems[item_count]);

并且在 displayInventory() 中，您将所有 display[i].xxx 更改为 display[i]->xxx。