VLA和通过malloc分配动态内存之间有什么区别? [英] What's the difference between a VLA and dynamic memory allocation via malloc?

问题描述

我对此很好奇:

两者之间的区别是什么?

What is the diference between:

const int MAX_BUF = 1000;
char* Buffer = malloc(MAX_BUF);

和:

char Buffer[MAX_BUF];

推荐答案

• 情况1:在

  • Case 1: In

     char Buffer[MAX_BUF];
    

    Buffer是大小为MAX_BUF的 数组 .分配技术称为 VLA .

    情况2:在

    const int MAX_BUF = 1000;
    char* Buffer = malloc(MAX_BUF);
    

    Buffer是 指针 ，它分配了大小为MAX_BUF的内存，该内存为1000.

    Buffer is a pointer which is allocated a memory of size MAX_BUF which is 1000.

    ，并且数组与指针不相同，并且 C-FAQ有一个很好的收藏，详细说明了原因.

    and, an array is not the same as a pointer, and C-FAQ has a Very Good collection detailing the reasons.

    就可用性和行为而言，主要区别在于:

    The major difference, in terms of usability and behaviour are:

    1. (1)在堆栈上，通常是 ^Note ，而(2)总是在堆栈上.
    2. (1)分配后具有固定的大小，(2)可以调整大小.
    3. (1)是在调用封闭函数并具有块范围OTOH时分配的；(2)是在运行时动态分配的内存，并且返回的内存的生存期从分配到释放为止.
    4. (1)分配的内存无需由程序员管理，而在(2)中，所有malloc() d内存都应为free() d. ^{[礼貌:乔基 ]}
    1. (1) is on stack, usually ^Note, while (2) is on heap, always.
    2. (1) has fixed size once allocated, (2) can be resized.
    3. (1) is allocated when the enclosing function is called and has the block scope OTOH, (2) is allocated memory dynamically, at runtime and the returned memory has a lifetime which extends from the allocation until the deallocation.
    4. (1) allocated memory need not be managed by programmer, while in (2) all malloc()d memory should be free()d. ^{[Courtesy: Giorgi]}

    ---

    ^{注意: Wiki}

    ---

    ^{Note: Wiki}

    ^{例如，GNU C编译器为堆栈上的VLA分配内存.}

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