将 const char* 转换为 char*

Question

I'm always wondering about the complaint of the compiler when I declare and define a char*-variable.

char* myChar = "Char";

The compiler will complain that it cannot convert const char* to char*. It need an explicit conversion like

char* myChar = (char*)"Char";

My first question is if this is the correct way to initialize a char* with a const char*. And my second question is, why the compiler need this explicit conversion. I think there is no great difference between const char* and char* except the const.

Answer 1

On a technical level, there is a great difference between const MyType* and MyType* and it is easier to see in your example char* myChar = "Char"; in that the litteral string can be part of memory that may not be changed, but by assigning that to a non-const pointer, you say that you may well planning to change some characters anyway. That behavior is undefined. It may work and it may make your program stop unexpectedly and you can't even rule out any other behavior.

By casting (prefer const_cast in C++), you are saying to the compiler that you know what you're doing and you know better. The normal solution is const char* myChar = "Char"; or even const char* const myChar = "Char"; if you're not planning to point to other char arrays.

In C++, I find it even clearer working with std::string if you want to work with strings.

Answer 2

To the advanced programmer, there is definitely a great difference between const and non-const, in terms of integrity, security, and performance. We basically use const when we want to emphasize that a particular object/function/variable isn't allowed to be changed by the user.

check const correctness

The best-practice way to add/remove const/volatile modifiers is by using const_cast operator.

check The const_case operator