c语法总结

1.函数指针

#include <stdio.h>

int add(int a, int b)
{
	return a + b;
}

int sub(int a, int b)
{
	return a - b;
}

int main(void)
{
	int (*p) (int, int);
	p = add;
	printf("res is %d\n", p(5, 5));
	p = sub;
	printf("res is %d\n", p(5, 5));
	return 0;
}

2.指针函数

#include <stdio.h>
#include <stdlib.h>

char *alloc_space(int size)
{
	return (char *)malloc(size);
}

int main(void)
{
	char *p;
	p = alloc_space(100);
	printf("res is %d\n", p[99]);
	return 0;
}

3.void *

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
	void *p1;
	char *p2;
	int *p3;
	printf("size is %ld\n",sizeof(p1));
	printf("size is %ld\n",sizeof(p2));
	printf("size is %ld\n",sizeof(p3));
	p1=malloc(4);
	memset(p1,0x1,4);
	p2=p1;
	printf("value is 0x%x\n",*p2);
	p3=p1;
	printf("value is 0x%x\n",*p3);
	return 0;
}

size is 8
size is 8
size is 8
value is 0x1
value is 0x1010101