Pybind11: clang++ warning (self-assign-overloaded) for `py::self -= py::self`

Created on 24 Aug 2019 · 4Comments · Source: pybind/pybind11

Consider the following code (slightly modified version of the Operator overloading example):

#include <string>
#include <pybind11/operators.h>
namespace py = pybind11;

class Vector2 {
public:
    Vector2(float x, float y) : x(x), y(y) { }

    Vector2& operator+=(const Vector2 &v) { x += v.x; y += v.y; return *this; }
    Vector2& operator-=(const Vector2 &v) { x -= v.x; y -= v.y; return *this; }

private:
    float x, y;
};

PYBIND11_MODULE(example, m) {
    py::class_<Vector2>(m, "Vector2")
        .def(py::init<float, float>())
        .def(py::self += py::self)
        .def(py::self -= py::self);
}

When compiled with Clang 8.0.1 (on Arch Linux), this leads to the following warning:

$ clang++ -Wall example.cpp -o example.so -shared -fPIC -I ~/.local/include/ -I /usr/include/python3.7m/ -lpython3.7m
example.cpp:20:23: warning: explicitly assigning value of variable of type 'const
      pybind11::detail::self_t' to itself [-Wself-assign-overloaded]
        .def(py::self -= py::self);
             ~~~~~~~~ ^  ~~~~~~~~
1 warning generated.

Strangely enough, there is no warning for the operator+= overload. The same warning happens also for operator/=, but not for operator*=.

What shall we do about this (since libraries should not trigger compiler warnings)?

Source