C: conflicting types error

Question

I want to check a linked List of Elements holding an Integer each, if a value is already inside.

struct ListenElement{
    int wert;
    struct ListenElement *nachfolger;
};

struct ListenAnfang{
    struct ListenElement *anfang;
};

struct ListenAnfang LA;

bool ckeckForInt(int value){
    if (LA.anfang == NULL){
        return 0;
    }
    return checkCurrent(LA.anfang, value);
}

bool checkCurrent(struct ListenElement* check, int value){
    if (check->wert == value){
        return true;
    }
    else if (check->nachfolger != NULL){
        return checkCurrent(check->nachfolger, value);
    }
    else{
        return false;
    }   
}

Im getting a conflicting types for the checkCurrent Method, but can't find it.

Answer 1

Is missing the function declaration. In C, you need to declare the function, exactly as it is.

struct ListenElement{
    int wert;
    struct ListenElement *nachfolger;
};

struct ListenAnfang{
    struct ListenElement *anfang;
};

struct ListenAnfang LA;

//The function declaration !
bool checkCurrent(struct ListenElement* check, int value);

bool ckeckForInt(int value){
    if (LA.anfang == NULL){
        return 0;
    }
    return checkCurrent(LA.anfang, value);
}

bool checkCurrent(struct ListenElement* check, int value){
    if (check->wert == value){
        return true;
    }
    else if (check->nachfolger != NULL){
        return checkCurrent(check->nachfolger, value);
    }
    else{
        return false;
    }   
}

Answer 2

checkCurrent() is used before it is declared, or defined, which results in an implicit function declaration being generated with a return type of int (which is not the same as the definition of the function which has return type bool). Add a declaration for checkCurrent() prior to its first use:

bool checkCurrent(struct ListenElement* check, int value);

bool ckeckForInt(int value){
    if (LA.anfang == NULL){
        return false; /* Changed '0' to 'false'. */
    }
    return checkCurrent(LA.anfang, value);
}

or move its definition prior to checkForInt().