问题
c++14 provides variable templates Which work fine in visual-studio-2017, but within lambdas they seem to fall apart. For example:
template <typename T>
const auto PI = std::acos(static_cast<T>(-1));
int main() {
auto func = []() { cout << PI<float> << endl; };
func();
}
On gcc 6.3 this outputs:
3.14159
On Visual Studio 2017 this outputs:
0.0
回答1:
Wierd bug, but it seems to have a reliable workaround, which works for both, this case and the related case. In both cases forcefully activating template seems to do the job in VS2017:
template <typename T>
const auto PI = std::acos(static_cast<T>(-1));
int main()
{
PI<float>; // <------ this
auto func = []() { std::cout << PI<float> << std::endl; };
func();
}
GCC 6.3 for example: https://ideone.com/9UdwBT
来源：https://stackoverflow.com/questions/49117293/templated-variables-bug-with-lambdas-in-visual-studio