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Asked: 2026-05-25T09:44:51+00:00

I have a piece of code that pretty much reduces down to: template<class T>

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I have a piece of code that pretty much reduces down to:

template<class T> struct MyStruct;  // No definition by default
template<class T> struct MyStruct<T *> { ... };  // Specialization for pointers

Now somewhere in my code, I’m getting an instantiation of MyStruct<T> that happens to be undefined (no C++0x/011, no Boost… nothing fancy, just plain C++03):

error C2027: use of undefined type 'MyStruct<T>'

The trouble is, I have no idea where this is being caused, because the code that’s doing the instantiation is itself a template, and called from numerous places, with different arguments.

Is there a way to somehow figure out what T is at compile-time, so I can understand the error messages better?

(Sorry, I forgot to mention: Visual Studio 2008.)

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1 Answer

  1. Editorial Team

    I believe you’re using MSVC++, if so, then see the output window, it might have more info printed, especially the line number along with the filename. Once you know the file and line number, you can start from there.

    Output window usually prints everything, like how and with what template argument(s), a template is instantiated. Everything step by step. Those messages are very useful when debugging.

    As you found yourself, enabling /WL prints more detail messages in the output window.

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