How do I initialize a pointer to an array of pointers?

Question

I am trying to initialize a pointer to an array of pointers. Here's an example:

class MyClass { };
// INTENT: define a pointer to an array of pointers to MyClass objects
MyClass* (*myPointer)[];
int main(void) {
 // INTENT: define and initialize an array of pointers to MyClass objects
 MyClass * tempArray [] = {
 new MyClass(),
 new MyClass()
 };
 // INTENT: make myPointer point to the array just created
 myPointer = tempArray;
}

When I compile this I get:

./test2.cpp: In function ‘int main()’:
./test2.cpp:15:19: error: cannot convert ‘MyClass* [2]’ to ‘MyClass* (*)[]’ in assignment
 myPointer = tempArray;
 ^~~~~~~~~

• Code-Apprentice: The compiler is complaining because myPointer and tempArray are different types. You can see this clearly in the declarations. You need to declare them both as the same type in order for the assignment to work.
• Code-Apprentice: Or you need to change the assignment statement. Perhaps myPointer = &tempArray is what you want?
• Thomas Matthews: Try using std::vector<MyClass *>. Vectors are a lot easier to deal with.
• Heath: I want to avoid vectors because this is an embedded project.
• Michael Dorgan: FYI - embedded is not a good excuse to avoid STL and containers...

Answer 1

First, arrays are not pointers. You have to use the address-of:

 myPointer = &tempArray;

Next, when you write

T foo[] = { t1, t2 };

this is just short-hand notation for

T foo[2] = { t1, t2 };

Either use the correct type (Live Example):

MyClass* (*myPointer)[2];

or perhaps better use a std::array<MyClass> in the first place. And forget about raw owning pointers. Use smart pointers instead.

• 463035818_is_not_an_ai: @NickReed fixed. I had to combine two wrong answers to get a correct one ;)
• Code-Apprentice: @NickReed That repl doesn't appear to be changed from the OP's code here.
• Nick Reed: Solid, have an upvote! Out of curiosity, would you happen to know why can't one convert between foo[] and foo[2]? I was trying to answer the question myself, but couldn't find the reasoning behind the compiler's hangup about that.
• 463035818_is_not_an_ai: @NickReed i have to admit, I have no clue what a foo[] (or MyClass* (*myPointer)[];) actually is

Answer 2

// INTENT: define a pointer to an array of pointers to MyClass objects
MyClass* (*myPointer)[];

You can't obmit the size of the array in declaration. You need this:

MyClass* (*myPointer)[2];

Then,

 MyClass * tempArray [] = {
 new MyClass(),
 new MyClass()
 };
 // INTENT: make myPointer point to the array just created 
 myPointer = &tempArray;

Answer 3

An array decays into a pointer to the first element. Since the element type is also a pointer, you can declare a variable that is a double-pointer and have it point at that element, eg:

class MyClass { };
MyClass** myPointer;
int main(void) {
 MyClass * tempArray [] = {
 new MyClass(),
 new MyClass()
 };
 myPointer = tempArray;
 // same as:
 // myPointer = &tempArray[0];
 ...
}

• Heath: BINGO Thank you. This is exactly what I needed!