Ç - 释放结构 [英] C - freeing structs

问题描述

让我们说我有这个结构

typedef struct person{
    char firstName[100], surName[51]
} PERSON;

和我分配由malloc空间，并与一些值填充它。

and I am allocating space by malloc and filling it with some values

PERSON *testPerson = (PERSON*) malloc(sizeof(PERSON));
strcpy(testPerson->firstName, "Jack");
strcpy(testPerson->surName, "Daniels");

什么是释放由该结构所采取的一切记忆的正确和安全的方式？是自由（testPerson）;足够的或者我需要一个释放的每个结构的属性吗？

What is the correct and safe way to free all memory taken by that struct? Is "free(testPerson);" enough or do I need to free each struct's attribute one by one?

这使我另一个问题 - 如何存储在内存中的结构？我注意到一个奇怪的现象 - 当我尝试打印结构地址是等于它的第一属性的地址

It leads me to another question - how are structures stored in memory? I noticed a strange behaviour - when I try to print structure address it's equal to it's first attribute's address.

printf("Structure address %d == firstName address %d", testPerson, testPerson->firstName);

这意味着，这个
    免费（testPerson）
应等于这
    免费（testPerson->的firstName）;

Which means that this free(testPerson) should be equal to this free(testPerson->firstName);

和这不是我想做的事情。

and that's not what I want to do.

感谢

推荐答案

答案很简单：免费（testPerson）足够

记住，你可以使用免费（）只有当您使用的malloc 分配的内存，释放calloc 或的realloc 。

Remember you can use free() only when you have allocated memory using malloc, calloc or realloc.

在你的情况，你有 testPerson 只malloc内存使释放的就足够了。

In your case you have only malloced memory for testPerson so freeing that is sufficient.

如果您已经使用的char *姓名，*最后姓然后在这种情况下存储姓名您必须分配的内存，这就是为什么你必须单独释放每个成员

If you have used char * firstname , *last surName then in that case to store name you must have allocated the memory and that's why you had to free each member individually.

下面也应该以相反的顺序的一个点;这意味着，分配给元素的记忆是如此免费（）首先然后释放指针对象。

Here is also a point it should be in the reverse order; that means, the memory allocated for elements is done later so free() it first then free the pointer to object.

舷每个元素你可以看到如下所示的演示：

Freeing each element you can see the demo shown below:

typedef struct Person
{
char * firstname , *last surName;
}Person;
Person *ptrobj =malloc(sizeof(Person)); // memory allocation for struct
ptrobj->fistname = malloc(n); // memory allocation for firstname
ptrobj->surName = malloc(m); // memory allocation for surName

.
. // do whatever you want

free(ptrobj->surName);
free(ptrobj->firstname);
free(ptrobj);

这背后的原因是，如果你释放 ptrobj 第一，那么就会出现内存泄漏是由姓和 suName 指针。

The reason behind this is, if you free the ptrobj first, then there will be memory leaked which is the memory allocated by firstname and suName pointers.

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