1 #include 
     
       2 #include 
      
        3 #define PR(n,...) printf("MSG"#n":"__VA_ARGS__) 4  5 int main(void) 6 { 7     double x = 48; 8     double y; 9 10     y = sqrt(x);11     PR(1,"x = %.2lf\n",x);12     PR(2,"x = %.2lf , y = %.4lf\n",x,y);13 14     return 0;15 }
      
     

gcc -E va.c

1 # 5 "va.c" 2 int main(void) 3 { 4  double x = 48; 5  double y; 6  7  y = sqrt(x); 8  printf("MSG""1"":""x = %.2lf\n",x); 9  printf("MSG""2"":""x = %.2lf , y = %.4lf\n",x,y);10 11  return 0;12 }

结果：

MSG1:x = 48.00MSG2:x = 48.00 , y = 6.9282