foo.c: In function 'main':
foo.c:7:8: error: size of array 'x' is too large
  float x[10000000000], y[100000000000], length=0, totallength;
        ^
foo.c:7:24: error: size of array 'y' is too large
  float x[10000000000], y[100000000000], length=0, totallength;
                        ^
foo.c:7:24: warning: unused variable 'y' [-Wunused-variable]
foo.c:7:8: warning: unused variable 'x' [-Wunused-variable]
  float x[10000000000], y[100000000000], length=0, totallength;
        ^