---

Lỗi biên dịch:

Main.cc: In function ‘int main()’:
Main.cc:20:27: error: ‘pi’ was not declared in this scope
     printf("Pi = %0.8lf", pi);
                           ^~
Main.cc:20:27: note: suggested alternative: ‘Pi’
     printf("Pi = %0.8lf", pi);
                           ^~
                           Pi
Main.cc:19:12: warning: unused variable ‘Pi’ [-Wunused-variable]
     double Pi = 4 * res;
            ^~
Main.cc:6:10: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%lf", &c);
     ~~~~~^~~~~~~~~~~