/in/foo.cc: In function 'void read(int&)':
/in/foo.cc:12:17: warning: 'ch' is used uninitialized in this function [-Wuninitialized]
     while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
           ~~~~~~^~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:11:22: warning: 'ch' may be used uninitialized in this function [-Wmaybe-uninitialized]
     int f=1;x=0;char ch;
                      ^~