c4102.cpp

// Copyright Glen Knowles 2017 - 2021.
// Distributed under the Boost Software License, Version 1.0.
//
// c4102.cpp - bugs msvc2017
//
// Compile with: Visual C++ 2017 Version 15.3.2
//
// When "if constexpr" condition is false the references to goto labels
// in the statement block aren't (but should be) considered before reporting
// C4102 "unreferenced label" and C4702 "unreachable code".

using namespace std;

//===========================================================================
template<bool Flag>
bool test() {
    if constexpr (Flag)
        goto TRUE;

    return false;

TRUE:
    return true;
}

//===========================================================================
int main(int, char * []) {
    // Call to test<0>() compiles with improper warning:
    //
    // c4102.cpp(23): warning C4102: 'TRUE': unreferenced label
    // c4102.cpp(35): note: see reference to function template instantiation
    //   'bool test<0>(void)' being compiled
    test<0>();

    // This call compiles cleanly - as it should
    test<1>();
}