C++ discards qualifiers

Question

I have this error:

BSPArduino.cpp:316: error: passing 'const BSPArduino' as 'this' argument of 'virtual void BSPArduino::enableWdt(const WATCHDOG_TIMER_DELAY&, const ___bool&)' discards qualifiers

This method is define like this:

void BSPArduino::enableWdt(const WATCHDOG_TIMER_DELAY &delay, const ___bool &enable)

I want to call it like this:

enableWdt(this->watchdogTimer, ___false);

With:

WATCHDOG_TIMER_DELAY watchdogTimer;

Why do I have this build error?

Cutshall

The calling context is const (eg void f() const { ... } ) – Leslileslie

You're calling a non-const method with an object that's const. – Kyd

Answer 1

BSPArduino::enableWdt() is a non-const method. If you try and call a non-const method from a const one you will get this error.

Essentially the error is trying to tell you that you are discarding the constness of "this".

Stays

The word of the day is... constness! Often used when describing adherence to const correctness. – Metathesize

Answer 2

You're trying to call a non-const function from a const member function; that's not allowed.

If possible, add a const qualifier to enableWdt. If that's not possible (because it modifies the object) then you'll have to either remove the const qualifier from the calling function, or restructure the code so that enableWdt is called from somewhere else.

Grivet