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It is legal to convert a pointer-to-non-const to a pointer-to-const.
Then why isn't it legal to convert a pointer to pointer to non-const to a pointer to pointer to const?
E.g., why is the following code illegal:
char *s1 = 0; const char *s2 = s1; // OK... char *a[MAX]; // aka char ** const char **ps = a; // error! 
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A pointer to a const value (sometimes called a pointer to const for short) is a (non-const) pointer that points to a constant value. In the above example, ptr points to a const int . Because the data type being pointed to is const, the value being pointed to can't be changed. We can also make a pointer itself constant.
The pointer argument '%argument%' for function '%function%' can be marked as a pointer to const (con. 3). A function with a T* argument has the potential to modify the value of the object. If that is not the intent of the function, it is better to make the pointer a const T* instead.
From the standard:
const char c = 'c'; char* pc; const char** pcc = &pc; // not allowed *pcc = &c; *pc = 'C'; // would allow to modify a const object If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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