C++ Error: Incompatible types in assignment of ‘char*’ to ‘char [2]

c++, char, error-handling

Solution

Raw arrays in C++ are kind of annoying and fraught with peril. This is why unless you have a very good reason to you should use `std::vector` or `std::array`.

First off, as others have said, `char[2]` is not the same as `char*`, or at least not usually. `char[2]` is a size 2 array of `char` and `char*` is a pointer to a `char`. They often get confused because arrays will decay to a pointer to the first element whenever they need to. So this works:

char foo[2];
char* bar = foo;

But the reverse does not:

const char* bar = "hello";
const char foo[6] = bar; // ERROR

Adding to the confusion, when declaring function parameters, `char[]` is equivalent to `char*`. So in your constructor the parameter `char short_name[2]` is really `char* short_name`.

Another quirk of arrays is that they cannot be copied like other types (this is one explanation for why arrays in function parameters are treated as pointers). So for example I can not do something like this:

char foo[2] = {'a', 'b'};
char bar[2] = foo;

Instead I have to iterate over the elements of `foo` and copy them into `bar`, or use some function which does that for me such as `std::copy`:

char foo[2] = {'a', 'b'};
char bar[2];
// std::begin and std::end are only available in C++11
std::copy(std::begin(foo), std::end(foo), std::begin(bar));

So in your constructor you have to manually copy the elements of `short_name` into `short_name_`:

Territory::Territory(std::string name, char* short_name, Player* owner, 
                     char units) : name_(name), owner_(owner), units_(units)
{ 
    // Note that std::begin and std::end can *not* be used on pointers.
    std::copy(short_name, short_name + 2, std::begin(short_name));
}

As you can see this is all very annoying, so unless you have a very good reason you just should use `std::vector` instead of raw arrays (or in this case probably `std::string`).

Problem

Original source