C语言中指向指针的指针

C语言中指向指针的指针

#include <stdio.h>

int main()
{
	int a = 1;
	int* p = NULL;
	int** pp = NULL;

	pp = &p;

	*pp = &a;// ==> p = &a;

	printf("%d", **pp);

	return 0;
}

使用实例：重置动态空间大小（类似于在函数中修改入参）

#include <stdio.h>

int reset(char**p, int size, int new_size)
{
	int ret = 1;
	int i = 0;
	int len = 0;
	char* pt = NULL;
	char* tmp = NULL;
	char* pp = *p;

	if( (p != NULL) && (new_size > 0))
	{
		pt = (char*)malloc(new_size);

		tmp = pt;

		len = (size < new_size) ? size : new_size;

		for( i=0; i<len; i++)
		{
			*tmp++ = *pp++;
		}

		free(*p);
		*p = pt;
	}

	return ret;
}

int main()
{
	char* p = (char*)malloc(5);
	printf("%0X\n", p);

	if( reset(&p, 5, 3)	)
	{
		printf("%0X\n", p);
	}
	return 0;
}