/in/foo.cc: In function 'int IO::read()':
/in/foo.cc:24:17: warning: 'ch' is used uninitialized in this function [-Wuninitialized]
   for(; !isdigit(ch) ; ch = getchar());
          ~~~~~~~^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:24:17: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(; !isdigit(ch) ; ch = getchar());
          ~~~~~~~^~~~
/in/foo.cc:22:8: note: 'ch' was declared here
   char ch;
        ^~
/in/foo.cc:24:17: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(; !isdigit(ch) ; ch = getchar());
          ~~~~~~~^~~~
/in/foo.cc:22:8: note: 'ch' was declared here
   char ch;
        ^~
/in/foo.cc:24:17: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(; !isdigit(ch) ; ch = getchar());
          ~~~~~~~^~~~
/in/foo.cc:22:8: note: 'ch' was declared here
   char ch;
        ^~
/in/foo.cc:24:17: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
   for(; !isdigit(ch) ; ch = getchar());
          ~~~~~~~^~~~
/in/foo.cc:22:8: note: 'ch' was declared here
   char ch;
        ^~