/in/foo.c:2:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
/in/foo.c: In function 'main':
/in/foo.c:6:7: error: 'a' undeclared (first use in this function)
     c=a+b;
       ^
/in/foo.c:6:7: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:9: error: 'b' undeclared (first use in this function)
     c=a+b;
         ^
/in/foo.c:7:5: warning: implicit declaration of function 'print' [-Wimplicit-function-declaration]
     print("%d",c);
     ^~~~~