Constexpr variable and division

Question

I\'m trying to evaluate this simple expression at compile time using C++11 new constexpr feature:

template 
class Test
{
   static constexpr          


        

Answer 1

Solved. One of the template instance had b=0. Somehow, Clang didn't warn me I was dividing by zero. And +Inf is not a constant expression.

Answer 2

The reason why:

Test<10,0> test1 ;

fails is because you have undefined behavior due to division by zero. This is covered in the draft C++ standard section 5.6 [expr.mul] which says:

If the second operand of / or % is zero the behavior is undefined

and constant expressions specifically exclude undefined behavior. I am not sure what version of clang you are using but the versions I have available online do provide a divide by zero warning (see it live):

note: division by zero
static constexpr double c = a / b;
                              ^