C++ freeRTOS Task, invalid use of non-static member function

Question

Where is the Problem?

void MyClass::task(void *pvParameter){
     while(1){
         this->update();
     }
}

void MyClass::startTask(){
    xTaskCreate(this->task, "Task", 2048, NULL, 5, NULL);
}

But, I get this:

error: invalid use of non-static member function

I cannot find any useful doc to check where is the mistake,
but i think that should be something like: (C++11's std::thread) e.g.:

xTaskCreate(&MyClass::task, "Task", 2048, (void*)this, 5, NULL);

solution that works for me:

void MyClass::task(){
    while(1){
        this->update();
    }
}

static void MyClass::startTaskImpl(void* _this){
    static_cast<MyClass*>(_this)->task();
}

void MyClass::startTask(){
    xTaskCreate(this->startTaskImpl, "Task", 2048, this, 5, NULL);
}

`this->task` is not valid if `task` is a non-static member function. — user253751, Aug 23 '17 at 05:24

score 12 · Accepted Answer · answered Aug 23 '17 at 10:15

I use this pattern with a wrapper function for instanciating pthread with non-static member functions. The function called in xTask is a static member function, calling the task function using void* pointer. MyClass.hpp :

class MyClass {
    public:
        MyClass() {}
        ~MyClass() {}
    private:
        void update();
        void task();
        static void startTaskImpl(void*);
        void startTask();
 }

MyClass.cpp :

void MyClass::task(){
     while(1){
         this->update();
     }
}

void MyClass::startTaskImpl(void* _this){
    (MyClass*)_this->task();
}
void MyClass::startTask(){
    xTaskCreate(this->startTaskImpl, "Task", 2048, this, 5, NULL);
}

If you get `error: 'void*' is not a pointer-to-object type` try changing `(MyClass*)_this->task();` to `((MyClass*)_this)->task();` — b264, Aug 25 '23 at 21:43

score 2 · Answer 2 · answered Aug 23 '17 at 07:14

2

According to this FreeRTOS official thread, you can write wrapper function to achieve this.

answered Aug 23 '17 at 07:14

Azeem

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C++ freeRTOS Task, invalid use of non-static member function

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