How to use malloc in c language

malloc is a function in C language used to dynamically allocate memory in heap memory. The syntax is void *malloc(size_t size). It returns a pointer to the allocated memory on success and NULL on failure. Usage includes: 1. The required memory size cannot be determined at compile time; 2. Memory requirements will change as the program executes; 3. A non-contiguous memory block is required. The allocated memory must be released using the free function to prevent memory leaks.

Usage of malloc in C language

What is malloc?

malloc is a function in the C language standard library that is used to dynamically allocate memory in the heap memory.

Syntax

<code class="c">void *malloc(size_t size);</code>

• size: The number of bytes to allocate.

Return type

• Returns a pointer to the allocated memory on success and NULL on failure.

Purpose

malloc is used to dynamically allocate memory while the program is running. This is useful for situations where the required memory size cannot be determined at compile time.

Memory requirements will change as the program executes.
• Requires a non-contiguous block of memory (i.e. not all memory is contiguous).
• Usage example

<code class="c">int *ptr = (int *)malloc(sizeof(int) * 10);
if (ptr == NULL) {
  // 内存分配失败，处理错误
}

// 使用分配的内存
...

// 释放分配的内存
free(ptr);</code>

Release allocated memory

After using the allocated memory, you must use free function releases it. If not released, the program will leak memory.

<code class="c">free(ptr);</code>

Note

The memory allocated by malloc comes from the heap, which is different from the stack memory. Heap memory is not limited by function scope.

If the requested memory cannot be allocated, malloc will return NULL.
• After release, the pointer will no longer point to valid memory, and using it again will cause the program to crash.
• It is recommended to use free to release memory instead of directly using pointers to release memory.

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