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C++ pointer to const pointer


C++ pointer to const pointer

By : Linny
Date : October 28 2020, 08:00 PM
hope this fix your issue I always read C/C++ definitions from the right-most variable name leftwards.
So:
code :


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Why cant I pass a non const pointer to a function taking a reference to a pointer to a const as its argument

Why cant I pass a non const pointer to a function taking a reference to a pointer to a const as its argument


By : shraddha sawant
Date : March 29 2020, 07:55 AM
Hope this helps Here's a code snippet that hopefully conveys what I'm trying to do: , Supposing that you could do it, you could write the following:
code :
const int c = 0;

void updatePointer(const int* &i) {
    i = &c;
}

int main() {
    int *ptr;
    updatePointer(ptr);
    *ptr = 1; // attempt to modify the const object c, undefined behavior
}
What's wrong with defining a reference to a pointer to a const data with non-const pointer?

What's wrong with defining a reference to a pointer to a const data with non-const pointer?


By : albert velasco
Date : March 29 2020, 07:55 AM
Does that help
code :
const int x = 1;
int* p;
const int*& r = p;
r = &x;
*p = 2;
Why is conversion from const pointer-to-const to const pointer-to-nonconst in an initializer list allowed

Why is conversion from const pointer-to-const to const pointer-to-nonconst in an initializer list allowed


By : Daniel Olivares
Date : March 29 2020, 07:55 AM
will be helpful for those in need Your assumptions are incorrect. Taking them one at a time, first code annotation.
code :
class Cheater
{
public:
    Cheater(int avalue) :
        value(avalue),
        cheaterPtr(this) // NOTE: perfectly legal, as *this is non-const
                         // in the construction context.
    {}

    // NOTE: method is viable as const. it makes no modifications
    //  to any members, invokes no non-const member functions, and
    //  makes no attempt to pass *this as a non-const parameter. the
    //  code neither knows, nor cares whether `cheaterPtr`points to
    //  *this or not.
    Cheater& getCheaterPtr() const {return *cheaterPtr;}

    int value;

private:
    Cheater * cheaterPtr; // NOTE: member pointer is non-const.
};


int main()
{
    // NOTE: perfectly ok. we're creating a const Cheater object
    //  which means we cannot fire non-const members or pass it
    //  by reference or address as a non-const parameter to anything.
    const Cheater cheater(7);

    // NOTE: completely lega. Invoking a const-method on a const
    // object. That it returns a non-const reference is irrelevant
    // to the const-ness of the object and member function.    
    cheater.getCheaterPtr().value = 4;

    return 0;
}
How to define array type in C and making it a const pointer (not pointer to const)

How to define array type in C and making it a const pointer (not pointer to const)


By : Carlos Andrade
Date : March 29 2020, 07:55 AM
wish of those help If you absolutely need have to have an typedef, use struct to to encapsulate it. Using typedef on arrays is not a good idea.
code :
typedef struct {
    int arr[123];
} array_t;
void someFunction(array_t * const myArray)
{
    myArray->arr[0] = ...
c++ const member function that returns a const pointer.. But what type of const is the returned pointer?

c++ const member function that returns a const pointer.. But what type of const is the returned pointer?


By : user3932043
Date : March 29 2020, 07:55 AM
should help you out I don't know what book you have read, but if you mark a method const it means that this will be of type const MyClass* instead of MyClass*, which in its turn means that you cannot change nonstatic data members that are not declared mutable, nor can you call any non-const methods on this.
Now for the return value.
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