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How to init this static var

May 11, 2025 at 8:30am
Laurent7601 (20)
Hi!
I've a template class Application which have a static var. (a pointer to the application instance)

I declare it like this :

static Application<A, T>* app;

I initialize it in the c++ file :

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#include "../../../include/odfaeg/Graphics/application.h"
namespace odfaeg {
    namespace core {
        using namespace sf;
        template<typename A, typename T>
        Application<A, T>* Application<A, T>::app = nullptr;
        template<typename A, typename T>
        Clock Application<A, T>::timeClk = Clock();
    }
}


My library compiles fine but when I compile my project using my lib, I get this undefined reference error from the linker :

 
 
C:\mingw64\bin\..\lib\gcc\x86_64-w64-mingw32\14.2.0\..\..\..\..\x86_64-w64-mingw32\bin\ld.exe: obj\Debug\ODFAEG-master\Demos\ODFAEG-DEMO\application.o:application.cp:(.rdata$.refptr._ZN6odfaeg4core11ApplicationIN6sorrok7MyAppliENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEE3appE[.refptr._ZN6odfaeg4core11ApplicationIN6sorrok7MyAppliENSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEE3appE]+0x0)||undefined reference to `odfaeg::core::Application<sorrok::MyAppli, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >::app'|


what's wrong ?
Thanks.
Last edited on May 11, 2025 at 8:32am
May 11, 2025 at 8:37am
Laurent7601 (20)
May 11, 2025 at 8:41am
Peter87 (11251)
Templates need to be defined in the header file (unless you add explicit template instantiations for all template arguments that you plan to use).
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