Created attachment 40032 [details]
c++ code

The following code generates a "internal compiler error: Segmentation fault". Code and gcc trace attached.

If I specify that `f` is `constexpr`, then there is not a segmentation fault. This code began as an attempt to identify at compile time if a given expression can be treated as a constant expression, but here I have simplified it. (The full code worked in clang in the manner that I expected. See http://stackoverflow.com/a/40413051/146041 for more on the context.)

My hunch is that 'f' is the problem here. It is being used in the computation of the return type of the generic lambda. In this particular codebase, I would expect a conventional refusal to compile with an error message about the fact that a constant expression is necessary as the non-type int parameter to the template Void.


//  g++ (GCC) 6.2.0

struct X {
    static constexpr int foo (int b) {
        return b;
    }
};

template<int>
using Void = void;

template<typename F,typename A>
auto
bar(F f, A a) -> decltype( ( f(a) , 0 ) )
{ return {}; }


int main() {
    //constexpr
        int f = 3;
    (void)f;
    auto l = [](auto of_type_X)->
           Void<(decltype(of_type_X)::   foo(f)   ,0)>{return;};
    bar( l , X{});
}