Error del compilador de la función constexpr C ++ 11 con el operador condicional ternario (? :)

Question

Aug 14, 2013, 02:20 PM

constexpr recursion ternary-operator c++11 c++

Error del compilador de la función constexpr C ++ 11 con el operador condicional ternario (? :)

¿Qué está mal con este pedazo de código?

#include <iostream>

template<unsigned int N, unsigned int P=0>
constexpr unsigned int Log2() {
    return (N <= 1) ? P : Log2<N/2,P+1>();
}

int main()
{
    std::cout << "Log2(8) = " << Log2<8>() << std::endl;
    return 0;
}

Al compilar congcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5), Obtuve el siguiente error:

log2.cpp: In function ‘constexpr unsigned int Log2() [with unsigned int N = 0u, unsigned int P = 1023u]’:
log2.cpp:5:38: error: template instantiation depth exceeds maximum of 1024 (use -ftemplate-depth= to increase the maximum) instantiating ‘constexpr unsigned int Log2() [with unsigned int N = 0u, unsigned int P = 1024u]’
log2.cpp:5:38:   recursively instantiated from ‘constexpr unsigned int Log2() [with unsigned int N = 4u, unsigned int P = 1u]’
log2.cpp:5:38:   instantiated from ‘constexpr unsigned int Log2() [with unsigned int N = 8u, unsigned int P = 0u]’
log2.cpp:10:37:   instantiated from here