求教：error: field ‘start’ has incomplete type

[tianzhengning]

#include <stdio.h>
#include <time.h>
struct A
{
	struct timeval start;
};
int main(int argc, char **argv)
{
	printf("hello world\n");
	return 0;
}

error: field ‘start’ has incomplete type

[qq120848369]

#include <sys/time.h>