Does GCC 7.3 omit the [[nodiscard]] attribute for reference returning member functions?

Question

I've got the following code utilizing the [[nodiscard]] attribute of C++17 .

class SomeClass {
public: /** Methods **/
    [[nodiscard]] int getValue()  { return n; }
    [[nodiscard]] int &getRef()   { return n; }
    [[nodiscard]] int *getPtr()   { return &n; }

private: /** Members **/
    int n{5};
};

int main() 
{
    SomeClass object;

    object.getValue();
    object.getRef();
    object.getPtr();

    return 0;
}

When I compile it with GCC 7.3 , I've two warnings stating that the return value of two functions is ignored. The two functions detected by the compiler are the ones that don't return a reference, getValue() and getPtr() .

On the other hand, when compiled with GCC 8.1 and above versions, the getRef() also causes a warning.

The C++ support table provided by GCC shows that the [[nodiscard]] attribute is fully supported as of version 7. It also has a white paper .

Appearance of a [[nodiscard]] call as a potentially evaluated discarded value expression is discouraged unless explicitly cast to void.

So, is it a bug or am I missing something?

Answer 1

Yes, it is a bug. It was fixed in GCC 8 as you have already realized.

Bug report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80896