foo.c: In function 'main':
foo.c:8:8: warning: iteration 17 invokes undefined behavior [-Waggressive-loop-optimizations]
    8 |  { a[i]=a[i-2]+a[i-1];
      |    ~~~~^~~~~~~~~~~~~~
foo.c:7:10: note: within this loop
    7 |  while (i<=19)
      |         ~^~~~
foo.c:12:19: warning: iteration 19 invokes undefined behavior [-Waggressive-loop-optimizations]
   12 |   sum=sum+1.0000/a[i];
      |                  ~^~~
foo.c:11:11: note: within this loop
   11 |  for(i=0;i<=19;i++)
      |          ~^~~~
foo.c:12:10: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
   12 |   sum=sum+1.0000/a[i];
      |       ~~~^~~~~~~~~~~~

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