realloc 用于重新分配内存的场景。如果原先通过 malloc分配的空间过小，则可通过realloc重新分配大小。当然具体实现的时候分两种情况，如果原内存块后有足够的空间，则之间将原内存块扩大，如果不够，则重新寻找一个地方，将原数据也拷贝至此。
代码：
#include <rtthread.h>
struct rt_thread thread1;
static rt_uint8_t thread1_stack[512];
void thread1_entry(void* parameter)
{
int i,j = 1;
char *ptr[10]; /* 用于放置10个分配内存块的指针*/
/* 对指针清零*/
for (i = 0; i <10; i ++)
ptr[i] = RT_NULL;
while(j--)
{
for (i = 0; i <10; i++)
{
/* 每次分配(1 <<i)大小字节数的内存空间*/
ptr[i] = rt_malloc(10);
/* 如果分配成功*/
if (ptr[i] != RT_NULL)
{
rt_kprintf("get memory: 0x%x\n", ptr[i]);
rt_realloc(ptr[i],16);
/* 如果分配成功*/
if (ptr[i] != RT_NULL)
{
rt_kprintf("memory realloc success!\n");
/* 释放内存块*/
rt_free(ptr[i]);
rt_kprintf("memory free success!\n");
ptr[i] = RT_NULL;
}
}
}
}
}
int rt_application_init()
{
rt_thread_init(&thread1,
"thread1",
thread1_entry, RT_NULL,
&thread1_stack[0], sizeof(thread1_stack),
10, 100);
rt_thread_startup(&thread1);
return 0;
}结果：
get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success! get memory: 0x20000c58 memory realloc success! memory free success!