GNU下的void指针#include <stdio.h>typedef enum{ red, green, blue,}color_type;static int choose(void *type_p);int main(int argc, char **argv){ void *void_p; /*test 1: size of void pointer and size of object void pointer points to*/ printf("Size of the void pointer is %d.\n", sizeof(void_p)); printf("Size of the pointed object is %d.\n", sizeof(*void_p) ); //result is 1. In GNU, void pointer is treated same as char pointer /*test 2: relation between void pointer and other type pointer*/ int var = 9; int *num_p = &var; void_p = num_p; *(int *)void_p = 10; printf("Value of the pointer object num_p is %d.\n", *num_p); printf("Value of the pointer object is %d.\n", *((int *)void_p)); //result is 9, Be care to cast it to other type pointer /*test 3: pass parameter to a function, */ choose(red); /*test 4: void pointer arithmetic, void pointer is treated same as char pointer*/ char a[5] = "abcd"; int i = 0; void_p = a; for(; i < 5; i++) {printf("Value of *(a)void_p is %c.\n", *(char *)void_p++); } return 0;}static int choose(void *type_p){ int type = (color_type)type_p; /*void type converts to enum type */ switch(type) { case 0: printf("You choose red!\n"); break; case 1: printf("You choose green!\n"); break; case 2: printf("You choose blue!\n"); break; } return 0;}
