/in/foo.c: In function 'main':
/in/foo.c:5:14: warning: missing braces around initializer [-Wmissing-braces]
  int m[2][2]={b1,a1,b2,a2};
              ^
/in/foo.c:5:14: note: (near initialization for 'm')
/in/foo.c:6:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(i=0;i<2;i++)
  ^~~
/in/foo.c:10:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   n/r==b1/a1+b2/a2;
   ^
/in/foo.c:10:6: warning: statement with no effect [-Wunused-value]
   n/r==b1/a1+b2/a2;
   ~~~^~~~~~~~~~~~~
/in/foo.c:11:15: warning: format '%d' expects a matching 'int' argument [-Wformat=]
   printf("%d/%d\n",n/r);
               ^
/in/foo.c:5:6: warning: 'b1' is used uninitialized in this function [-Wuninitialized]
  int m[2][2]={b1,a1,b2,a2};
      ^
/in/foo.c:5:6: warning: 'a1' is used uninitialized in this function [-Wuninitialized]
/in/foo.c:5:6: warning: 'b2' is used uninitialized in this function [-Wuninitialized]
/in/foo.c:5:6: warning: 'a2' is used uninitialized in this function [-Wuninitialized]
/in/foo.c:10:4: warning: 'n' is used uninitialized in this function [-Wuninitialized]
   n/r==b1/a1+b2/a2;
   ~^~
/in/foo.c:10:4: warning: 'r' is used uninitialized in this function [-Wuninitialized]