C ++ 2维静态数组与2维动态指针兼容

Question

Is there a way to declare 2 dimensional static array which is compatible with the dynamic pointer (TYPE**) ?

char strs1[2][256] = { "String 1", "String 2" }; // Static

What I want is to assign it to

char **strs2 = strs1;

Well, I can do something like that:

std::array<std::array<char, 256>, 2> arr = {"String 1", "String 2"};
char *temp[2] = { (char*)&arr[0], (char*) &arr[1] };
char **strs = (char**)temp;

cout << strs[0] << endl;
cout << strs[1] << endl;

// Output
String 1
String 2

But is there a better and simpler way to achieve the same result ?

Answer 1

char** can never be a way to reference a an array of arrays (there are no two-dimensional arrays in C/C++) because it doesn't have the information on the inner array size. In particular, there is no way compiler can generate a proper access code in following snippet:

char** arr = initialize_by_hack();
arr[2][4] = '42';

Here, to calculate second offset (4) compiler needs to know the size of element array - but is is nowhere in the code and not available.

Answer 2

No, you cannot change the fact that a two-dimensional array is incompatible with a T** .

You can only perform hacky workarounds like the one you posit in your question, or remedy the mistake or design flaw that initially led you to the requirement.

Since you're writing C++: why not use proper, modern, type-safe technologies rather than native arrays and a mess of pointers? A simple Matrix<T,W,H> class template that wraps a statically allocated T[W*H] but exposes two-dimensional indexing would be nice. Then just pass it around by reference (or, if you really must, by pointer).