How to use templates in a separate library?

[frame]

On Thursday, 23 June 2022 at 08:12:32 UTC, CrazyMan wrote:
> I have a separate library and some template interface in it
>
> ```d
> interface IFoo(T)
> {
>      void setValue(const(T) value);
> }
> ```
>
> But when using it in the main program, it throws a linking 
> error. I found that you can make a sourceLibrary that copies 
> the code instead of creating a binary. But with it, I also get 
> a linking error, and at the same time it is no longer 
> associated with my interface, but with a third-party dependency 
> (bindbc.opengl)
>
> What can I do to fix this?

This is insufficient information to help you.

- Separate library could mean multiple things: a compiler 
library, a static linked binary, a SO/DLL binary.

- What error is thrown?

- Are you using `extern` declarations?

For a successful build the linker needs to get all symbols from 
any referenced source. The template isn't an actual symbol, it's 
just a information for the compiler to generate one. It says 
nothing about the symbol will be really generated or not. Also 
the linker needs to know if a library has to be used.