modernc.org/ccgo/v3@v3.16.14/lib/testdata/gcc-9.1.0/gcc/testsuite/gcc.c-torture/execute/enum-2.c (about)

     1  /* Copyright (C) 2000 Free Software Foundation */
     2  /* by Alexandre Oliva  <aoliva@redhat.com> */
     3  
     4  enum foo { FOO, BAR };
     5  
     6  /* Even though the underlying type of an enum is unspecified, the type
     7     of enumeration constants is explicitly defined as int (6.4.4.3/2 in
     8     the C99 Standard).  Therefore, `i' must not be promoted to
     9     `unsigned' in the comparison below; we must exit the loop when it
    10     becomes negative. */
    11  
    12  int
    13  main ()
    14  {
    15    int i;
    16    for (i = BAR; i >= FOO; --i)
    17      if (i == -1)
    18        abort ();
    19  
    20    exit (0);
    21  }
    22