“undefined reference to”c++ template

You need to use the

export

keyword. However, I don't think G++ has proper support, so you need to include the template function's definition in the header so the translation unit can use it. This is because the

<int>

'version' of the template hasn't been created, only the

<typename T>

'version.'

An easy way is to

#include

the .cpp file. However, this can cause problems, e.g. when other functions are in the .cpp file. It will also likely increase the compile time.
A clean way is to move your template functions into its own .cpp file, and include that in the header
or

use the

export

keyword and compile it separately.
c++中template不支持声明和实现分别放在不同的文件中。可以通过include cpp文件解决这个问题。