In the below code I am trying to use CRTP to use the static member
"value" from the Child class in the Parent class. When compiling the
code with g++ 5.2.1 with the "-pedantic" flag, I am able to compile
without errors or warning, and on execution both c.print_value(); and
Child<int,4>::print_value(); print out 4.
However when compiling the same code with clang++3.7 or icc 14.0.3, I
encounter compilation failures. I have provided below the respective
compilation error prints, and have mailed the Clang mailing-list as well
to ask about this behaviour.
Would kindly request some insight into why this code work in GCC as
opposed to the other two compilers.
Best,
Dipto
------------------------------------------
#include <iostream>
template <typename DE>
struct Parent
{
static const int value = DE::value;
static void print_value ()
{
std::cout << "Value : " << value << '\n';
}
};
template <typename T, int N>
struct Child : Parent< Child<T,N> >
{
static const int value = N;
};
int
main ()
{
Child<int,4> c;
c.print_value();
Child<int,4>::print_value();
}
------------------------------------------
=====================================
Clang's Compilation errors
=====================================
crtp_clang_error.cpp:9:32: error: no member named 'value' in 'Child<int, 4>'
static const int value = DE::value;
~~~~^
crtp_clang_error.cpp:27:16: note: in instantiation of template class
'Parent<Child<int, 4> >' requested here
struct Child : Parent< Child<T,N> >
^
crtp_clang_error.cpp:38:16: note: in instantiation of template class
'Child<int, 4>' requested here
Child<int,4> c;
^
crtp_clang_error.cpp:40:3: error: no member named 'print_value' in
'Child<int, 4>'; did you mean 'Parent<Child<int, 4> >::print_value'?
Child<int,4>::print_value();
^~~~~~~~~~~~~~~~~~~~~~~~~
Parent<Child<int, 4> >::print_value
crtp_clang_error.cpp:11:15: note: 'Parent<Child<int, 4> >::print_value'
declared here
static void prnt_value ()
=======================================
ICC error
=======================================
error: incomplete type is not allowed
static const int value = DE::value;
^
detected during:
instantiation of class "Parent<DE> [with DE=Child<int, 4>]"
instantiation of class "Child<T, N> [with T=int, N=4]"
