Initialize a static const member with a template argument - c++

Question

I have a few lines that compile well on my system but don't compile on a colleagues system. That's why I would like to ask what the go-to solution for the problem would look like. I have to deal with a enum that implicitly defines how much space I have to provide for an std::array. Other parts of the code also make use of FooSize being static. (Optimization)
My current implementation looks like this
enum class FooType
{
ShortFoo,
LongFoo
};
// defined in a different file
template <FooType FType>
class FooContainer
{
public:
static const unsigned int FooSize {(FType == FooType::ShortFoo) ? 32 : 64 };
std::array<float, FooSize> fooArray;
};
The code seems to create issues on older llvm / clang compilers. 32 and 64 are actually provided via pre processor defines. I could just skip the FooType and use the size as an template argument but I would like to know what the most reliable method of initializing FooSize would be.

Answer 1

Your code seems correct to me and compile without problems with my olds g++ (4.9.2) and clang++ (3.5).
But, according the error message, could be that your compiler doesn't correctly support the C++11 declaration/initialization of static data members
I suggest you to try in the following way
template <FooType FType>
class FooContainer
{
public:
static const unsigned int FooSize;
std::array<float, FooSize> fooArray;
};
template <FooType FType>
int unsigned const FooContainer<FType>::FooSize
= ((FType == FooType::ShortFoo) ? 32 : 64);
or (I suppose is better)
template <FooType FType>
class FooContainer
{
public:
static const unsigned int FooSize {(FType == FooType::ShortFoo) ? 32 : 64 };
std::array<float, FooSize> fooArray;
};
template <FooType FType>
int unsigned const FooContainer<FType>::FooSize;
You can also try defining FooSize as constexpr instead of const.
Another solution could be transform FooSize in a template parameter
template <FooType FType,
std::size_t FooSize = (FType == FooType::ShortFoo) ? 32 : 64 >
class FooContainer
{
public:
std::array<float, FooSize> fooArray;
};