C++11 static_assert and template instantiation

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GCC is correct and the other compiler is correct too. Refer to 14.6p8 in the spec

If no valid specialization can be generated for a template definition, and that template is not instantiated, the template deļ¬nition is ill-formed, no diagnostic required.

Therefor, a compiler is free to reject the following

template<typename T>
void f() {
  static_assert(0, "may trigger immediately!");
  static_assert(sizeof(T) == 0, "may trigger immediately!");
}

If you want to go safe, you have to arrange it so the compiler cannot know until instantiation whether the boolean expression will be true or false. For example, get the value by getvalue<T>::value, with getvalue being a class template (one could specialize it, so the compiler cannot possibly know the boolean value already).

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