[ITK-dev] Problems with Change in itkStaticConstMacro

[Luc Hermitte]

Le 20/01/2016 09:57, Luc Hermitte a écrit :
> Hello,
> 
> Le 19/01/2016 21:19, Bradley Lowekamp a écrit :
>> Hello,
>>
>> My release builds for SimpleITK are having significant problems with the
>> change done here [1] to the itkStaticConstMacro.
>>
>> My builds on Redhat 5, with gcc 5.1, are filling my disk with errors
>> along the following:
>> [...]
> [...]

>> I’ll look into alternatives...
> 
> Can you isolate the error on a simple test case that reproduce the issue?

I've tried the file attached on https://ideone.com/SGlJ1i but it seems
valid with GCC 5.1.

However, in C++11, constexpr is required. And my g++ 4.8.2, and clang++
as well, tell me:

|| g++ -std=c++03 -Werror -Wall -pedantic    extern-templ.cpp   -o
extern-templ
extern-templ.cpp|19 col 24| error: ISO C++ 1998 forbids the use of
'extern' on explicit instantiations [-Werror=pedantic]
||  extern template struct Bar<Foo<int>, Foo<double> >;


What differs in SimpleITK source code?


--Luc
-------------- next part --------------
#include <iostream>
#if 0
#  define CONSTEXPR constexpr
#else
#  define CONSTEXPR 
#endif

template <typename T> struct Foo {
    typedef T Type;
    static const CONSTEXPR std::size_t k_Dim = sizeof(T);
};

template <typename I, typename O> struct Bar {
    static const CONSTEXPR std::size_t k_IDim = I::k_Dim;
    static const CONSTEXPR std::size_t k_ODim = O::k_Dim;
};

// declare
extern template struct Bar<Foo<int>, Foo<double> >;

// ----< end of .h

// define in one TU 
template struct Bar<Foo<int>, Foo<double> >;

// use, in another TU
int main ()
{
    typedef Bar<Foo<int>, Foo<double> > Type;
    std::cout << Type::k_IDim << " -- " << Type::k_ODim << "\n";
}