1 #include <stdio.h> 2 #include <math.h> 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 ",x); 12 PR(2,"x = %.2lf , y = %.4lf ",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 ",x); 9 printf("MSG""2"":""x = %.2lf , y = %.4lf ",x,y); 10 11 return 0; 12 }
结果：
MSG1:x = 48.00 MSG2:x = 48.00 , y = 6.9282