foo.c: In function 'main':
foo.c:15:13: warning: unused variable 'b' [-Wunused-variable]
   15 |         int b = 0;
      |             ^
foo.c: In function 'output':
foo.c:9:1: warning: control reaches end of non-void function [-Wreturn-type]
    9 | }
      | ^

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