/in/bigint.c: In function 'construct':
/in/bigint.c:44:6: error: implicit declaration of function 'pow' [-Werror=implicit-function-declaration]
   vv=pow(10,i-1);
      ^~~
/in/bigint.c:44:6: error: incompatible implicit declaration of built-in function 'pow' [-Werror]
/in/bigint.c:44:6: note: include '<math.h>' or provide a declaration of 'pow'
cc1: all warnings being treated as errors