static constexpr std::array 编译通过，运行错
extern "C"{
struct HEAD_MD002_4_T
{
static constexpr int _h[]= {5, 6, 8, 16, 16, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 11, 8, 12};
typedef std::tuple<string,string,string,int64_t,double,double,double,double> _FIELDS;
static constexpr std::array<int,sizeof(_h)> H = {5,12,21,38,55,67,79};
/*_HEAD_MD002_4()
{
std::partial_sum(std::begin(_h),std::end(_h),H.data(),[&](int x,int y){return x+y+1;});
}*/
};
}
//使用时
for(auto& i : HEAD_MD002_4_T::H)
{
//....
}
undefined symbol: _ZN14HEAD_MD002_4_T1HE)
编译正常，运行出错
另外一个问题是static constexpr std::array<int,sizeof(_h)> H 可不可以 利用 std::partial_sum进行初始化？
本帖最后由 sytpb 于 2016-12-13 16:59 编辑
extern "C"{
struct HEAD_MD002_4
{
// 1234 5 6 7 8 910 1112131415161718192021222324252627282930313233 3435
static constexpr int _h[]= {5, 6, 8, 16, 16, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 11, 8, 12};
typedef std::tuple<string,string,string,int64_t,double,double,double,double> _FIELDS;
static std::array<int,sizeof(_h)> H;
HEAD_MD002_4()
{
std::partial_sum(std::begin(_h),std::end(_h),H.data(),[&](int x,int y){return x+y+1;});
}
};
}
看了下，std::array 不属于literal type 所以不能定义成 constexpr .
这样也报类似错 第一条，既然H是static constexpr，那你有没有定义它呢？
#include <array>
struct HEAD_MD002_4_T
{
static constexpr int _h= {5, 6, 8, 16, 16, 11, 11, 11, 11, 11, 11, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 12, 11, 11, 8, 12};
static constexpr std::array<int,sizeof(_h)> H = {5,12,21,38,55,67,79};
};
constexpr int HEAD_MD002_4_T::_h;
constexpr std::array<int,sizeof(HEAD_MD002_4_T::_h)> HEAD_MD002_4_T::H;
int main( void )
{
for(auto& i : HEAD_MD002_4_T::H)
{
}
}
第二条，既然是 constexpr，怎么可以用 partial_sum 更改其值？而且 sizeof(_h) 是字节数吧，应该用 std::extent；而且既然是static，为什么在构造函数中初始化它？
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