3.3 C提高 指针 字符串

注意
//写内存时，一定要确保内存可写
	char *buf2 = "sadgkdsjlgjlsdk"; //文字常量区，内存不可改
	//buf2[2] = '1'; //err

	char buf3[] = "skgjkdsjgjds";
	buf3[1] = '1'; //ok

	char *p3 = NULL;
	//给p3指向的内存区域拷贝内存
	p3 = buf3;
	strcpy(p3, "1111"); //OK

void fun3(char **p /* out */, int *len)
{
	if (p == NULL)
	{
		return;
	}

	char *tmp = (char *)malloc(100);
	if (tmp == NULL)
	{
		return;
	}
	strcpy(tmp, "adlsgjldsk");

	//间接赋值
	*p = tmp;
	*len = strlen(tmp);


}
	//输入，主调函数分配内存
	char buf[100] = { 0 };
	fun(buf);
	printf("buf  = %s\n", buf);

	char *str = NULL;
	fun2(str);

	//输出，被调用函数分配内存，地址传递
	char *p = NULL;
	int len = 0;
	fun3(&p, &len);
	if (p != NULL)
	{
		printf("p = %s, len = %d\n", p, len);
	}