how to avoid warning in my own stack template

Question

Hi

I have tried to implement stack class as template type as below:
https://code.sololearn.com/cy3PSIom22ft

I am getting warning on the code for char* using on my stack implementation. Need your suggestion on the same in order to avoid warning.

Thanks in advance...!

Answer 1

Declaration of stack s
mystack<const char*> s;
change the static_casts to
static_cast<const char*>

Alternatively you can use
const_cast<char*> instead of static_cast

Answer 2

String literals are immutable so I believe the warnings here are useful.

You could use const_cast<type>(arg) to cast away the constness but I would advice against it. String literals are read-only and if they're modified the program will probably crash (or evoke undefined behavior).

The danger is that you could do something like this:
char *a = s.top()
*a = 'C';

If the stack accepts <const char *> the static casts are not needed, the warnings will go away and the compiler will complain if you try to modify the strings or assign them to a mutable datatype.

Answer 3

Both the option worked... I am confused now on immutable..

I generally used to modify the string as below:

string s = "welcome ";
string name = "Ketan";

s += name;

cout << s;

Isn't it good ? If so, what's best to do same?

Answer 4

Ketan Lalcheta

Yes that's fine. std::string is mutable because it copies the string literal into an internal buffer. "string literal" <-- like that one, is a const char * and is not mutable.
I think the confusion is due to the difference between char *, const char *, and std::string.

Answer 5

Okay Gen2oo , I updated and removed costantness by using const_cast while adding to stack...

Reason of same is that I wanted to allocate the memory in case of pointer data type...

However , I got confused with how to allocate memory...

template<typename T>
node<T>::node(T idata)
{
if(is_pointer<T>::value)
{
data = new static_cast<*T>;
}
data = idata;
}

I thought to add parametric constructor for node data addition. But how to do new operator is confusing me