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Subject: [Bug c++/55737] Template and the constant, short-form if-then-else condition issue
Date: Wed, 19 Dec 2012 15:54:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55737

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-12-19 15:54:22 UTC ---
(Your testcase would be a lot easier to read without all those comments inside
the conditional expression, I think it's safe to assume everyone here knows
which is the false branch of a conditional expression!)

A conditional expression is not a "static if" so  templates in both branches of
the conditional expression are instantiated, and instantiating DivByX<0> fails.

You could work around this by preventing instantiation of the problem case, the
simplest way is to specialize the template:

template <>
struct DivByX<0>
{
    enum
    {
        value1 = X,
        value2 = 0;
    };
};

Now it doesn't matter if the DivByX<0> case is instantiated because it doesn't
divide by zero.