[Bug c++/42810] Enumeration with sequential values has its for-loop exit condition optimized out.

["tony3 at GarlandConsulting dot us" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #18 from tony3 at GarlandConsulting dot us  2010-01-27 20:56 -------
Thanks for the correction - I missed that aspect.

However, a signed version of my simple example still upholds what I'm trying to
comment on: it behaves the same way regardless of optimization level (at least
as far as the loop exit is in view) -- a forever loop.

#include <stdio.h>
main()
{
    for (char i = 1 ; i <= 127 ; i++)
    {
        printf( "%d ", i);
    }
}

This program is always a forever loop, regardless of optimizer setting.  The
enumeration situation is not--which is my main point: trying to avoid
surprising unexpected changes in operation as one changes the optimizer
setting.

Incidentally, in the above program, the actual print results differ between -O0
and -O2. At -O0 the printed values increment up to 127 and then, as expected
change to -128 and count upwards.  At -O2 the values increment up to 127 and
then continue upward to huge positive integer values (e.g., I terminated the
test at 4101552 and counting).  It seems at -O2 that the value is no longer
considered 8-bit signed.

In any case, the forever loop remains a forever loop and doesn't morph into
anything radically different.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42810