Question

I have the following function in C++ :

char** f()
{
    char (*v)[10] = new char[5][10];
    return v;
}

Visual studio 2008 says the following:

error C2440: 'return' : cannot convert from 'char (*)[10]' to 'char **'

What exactly should the return type to be, in order for this function to work?

Answer 1

char** is not the same type as char (*)[10]. Both of these are incompatible types and so char (*)[10] cannot be implicitly converted to char**. Hence the compilation error.

The return type of the function looks very ugly. You have to write it as:

char (*f())[10]
{
    char (*v)[10] = new char[5][10];
    return v;
}

Now it compiles.

Or you can use typedef as:

typedef char carr[10];

carr* f()
{
    char (*v)[10] = new char[5][10];
    return v;
}

Ideone.

---

Basically, char (*v)[10] defines a pointer to a char array of size 10. It’s the same as the following:

 typedef char carr[10]; //carr is a char array of size 10

 carr *v; //v is a pointer to array of size 10

So your code becomes equivalent to this:

carr* f()
{
    carr *v = new carr[5];
    return v;
}

---

cdecl.org helps here:

• char v[10] reads as declare v as array 10 of char
• char (*v)[10] reads as declare v as pointer to array 10 of char