typeof()关键字

  1 #include <stdio.h>
  2 
  3 void func1(void)
  4 {
  5     int a = 1;
  6     typeof(int *)pa = &a;//pa的数据类型为int型的指针
  7 
  8     printf("pa:\t%p\n", pa);
  9     printf("&a:\t%p\n", &a);
 10     printf("a:\t%d\n", a);
 11     printf("*pa:\t%d\n", *pa);
 12 }
 13 
 14 void func2(void)
 15 {
 16     int b = 1;
 17     typeof(&b)pb = &b;//&b的数据类型为int*,所以pb的类型为int*。
 18 
 19     printf("pb:\t%p\n", pb);
 20     printf("&b:\t%p\n", &b);
 21     printf("b:\t%d\n", b);
 22     printf("*pb:\t%d\n", *pb);
 23 }
 24 
 25 void func3(void)
 26 {
 27     int* pc = NULL;
 28     typeof(*pc) c = 100;//pc的类型为int*,那么，*pc的类型即为int
 29     printf("c=%d\n",c);
 30 }
 31 
 32 void func4(void)
 33 {
 34     int i = 0;
 35     int* pc = NULL;
 36     typeof(*pc) arr[] = {1,2,3,4};//同样，*pc的类型为int
 37     for(i = 0; i < 4; ++i)
 38         printf("arr[%d]=%d\n", i, arr[i]);
 39 }
 40 
 41 void func5(void)
 42 {
 43     int i = 0;
 44     typeof(typeof(const char *)[4]) pchar = {"hello", "world", "good", "night"};
　　　　　//里层typeof的类型为const char*,和外层结合后，pchar的数据类型即为const char*指针数组
 45     for (i = 0; i < 4; i++)
 46         printf("pchar[%d]:%s\n", i, pchar[i]);
 47 }
 48 
 49 int add(int param1, int param2) 
 50 {
 51     return param1 + param2;
 52 }
 53   
 54 int sub(int param1, int param2)
 55 {
 56     return param1 - param2;
 57 }
 58   
 59 int mul(int param1, int param2) 
 60 {
 61     return param1 * param2;
 62 }
 63 
 64 void func6(void)
 65 {
 66     int (*func[3]) (int, int) = {add, sub, mul};//显然func的数据类型为函数指针数组，数组元素为函数指针。  
 67 
 68     typeof(func[0](1, 1)) sum = 100;  //func[0](1,1)===>add(1,1)===>2,即 typeof(2)sum = 100;
 69     typeof(func[1](1, 1)) dif = 101;  
 70     typeof(func[2](1, 1)) pro = 102;  
 71 
 72     printf("sum:%d\n", sum);  
 73     printf("dif:%d\n", dif);  
 74     printf("pro:%d\n", pro);
 75 }
 76 
 77 #define pointer(T)  typeof(T *)
 78 #define array(T, N) typeof(T[N])
 79 
 80 void func7(void)
 81 {
 82     int i = 0;
 83     array(pointer(char), 4) pchar = {"hello", "world", "good", "night"};
 84     for (i = 0; i < 4; i++)
 85         printf("pchar[%d]:%s\n", i, pchar[i]);
 86 }
 87 
 88 //from linux-3.5/include/linux/kernel.h 
 89 #define min(x, y) ({                 90     typeof(x) _min1 = (x);             91     typeof(y) _min2 = (y);             92     (void)(&_min1 == &_min2);         93     _min1 < _min2 ? _min1 : _min2; })
 94 
 95 
 96 int main(int argc, char** argv)
 97 {
 98     int a = 1;
 99     //char b = 2;
100     int b = 2;
101     func1();
102     func2();
103 
104     (void)12;
105 
106     printf("%d\n",min(a,b));
107     func3();
108     func4();
109     func5();
110     func6();
111     func7();
112 
113     return 0;
114 }