MXCHIP IoT DevKit too many initializers for 'unsigned char [0]

Question

Question

Trying to call the Display draw API using the sample code for the azure logo bitmap sample code. I'm unable to reach a point where I can the API because breaks when constructing the bitmap char arrays in my BMPManager class. I'm also testing custom bitmaps using this pixelcraft tool.

In file included from /Users/gregorydegruy/Code/GitHub/_mr.u/mxchip/Main.ino:5:0: sketch/srcsrc/BMPManager.cpp:4:2371: error: too many initializers for 'unsigned char [0]' unsigned char AzureBMP[] = {0,0,0,0,0,0,0,0,0,0,0,0, . . .

Main

void loop()
{
    Screen.print("start prgm...");
    delay(1000);
    Screen.draw(0, 0, 128, 8, bitMapManager.get_azure_bitmap());
    delay(5000);
    Screen.draw(0, 0, 128, 8, bitMapManager.get_nintendo_bitmap());
}

BMPManager

class BMPManager
{
    private:
        unsigned char AzureBMP[] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,128,192,192,224,240,56,12,192,240,224,192,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,128,224,224,224,224,128,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,192,224,248,252,254,255,255,63,15,3,64,248,254,255,255,255,255,255,252,248,224,128,0,0,0,0,0,0,0,0,0,0,0,0,0,0,128,240,252,127,31,3,3,15,127,254,240,192,0,0,0,0,8,28,28,28,28,156,220,252,124,60,28,0,0,0,252,252,248,0,0,0,0,0,0,252,252,248,0,0,0,0,252,252,252,112,56,28,28,28,0,128,224,240,248,28,28,12,12,28,248,248,240,128,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,128,224,248,252,255,255,255,255,63,15,3,0,0,0,0,0,0,3,7,15,31,63,127,255,255,255,255,255,252,240,224,128,0,0,0,0,0,0,64,112,124,127,31,7,7,7,7,7,7,7,7,31,127,126,120,64,0,96,112,120,126,127,103,99,97,96,96,96,0,0,0,63,127,127,240,224,224,96,96,56,127,127,127,0,0,0,0,127,127,127,0,0,0,0,0,0,15,63,127,123,243,227,227,227,227,99,99,35,3,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,1,0,8,8,8,8,8,12,12,12,12,12,14,14,14,14,14,15,15,15,15,15,15,15,15,15,15,12,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
        unsigned char NintendoSwitchBMP[] = { 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x80, 0xc0,0xc0,0xe0,0xe0,0xf0,0xf0,0xf8,0xf8, 0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8, 0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8, 0x00,0x00,0x00,0x00,0xf8,0xf8,0xf8,0xf8, 0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8,0xf8, 0xf8,0xf8,0xf0,0xf0,0xe0,0xe0,0xc0,0xc0, 0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0xc0,0xf0,0xfc,0xff,0xff, 0xff,0xff,0x7f,0x1f,0x0f,0x07,0x87,0x83, 0x83,0x81,0x81,0x81,0x81,0x81,0x01,0x01, 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    public:
        BMPManager() {}
        unsigned char* get_azure_bitmap() {
            return AzureBMP;
        }
        unsigned char* get_nintendo_bitmap() {
            return NintendoSwitchBMP;
        }
};

Answer 1

In C++ you are not allowed to declare non-static member arrays with unspecified size (empty []). Supplying an in-class brace-or-equal (BoE) initializer for such non-static member array does not override this rule

struct S
{
  int a[] = { 1, 2, 3 }; // <-- ERROR: `[]` array declaration is not allowed here
};

If you really need these arrays as non-static members of the class, you will have to explicitly specify their size (which is 1024 in your case). Once you do that, you will also be able to BoE initializers for them right inside the class definition

class BMPManager
{
private:
  unsigned char AzureBMP[1024] = { /* whatever */ };
  unsigned char NintendoSwitchBMP[1024] = { /* whatever */ };
  ...
};

The = is optional.

---

However, the real question in this case is whether you really need these arrays as non-static (and non-const) members of the class. Do you really need independent instances of these arrays in each instance of BMPManager class? Are these arrays supposed to be modifiable?

If you really need independent instances of such arrays in each object, then you will have to do what's shown above.

But if you don't need independent arrays in each object (which would probably also imply that the arrays are not supposed to change) then the proper way to go about it would be to declare them as static members

class BMPManager
{
private:
  static unsigned char AzureBMP[];          // static const ?
  static unsigned char NintendoSwitchBMP[]; // static const ?
  ...
};

and then define them in one of the .cpp files as

unsigned char BMPManager::AzureBMP[] = { /* whatever */ };
unsigned char BMPManager::NintendoSwitchBMP[] = { /* whatever */ };

Note that in this case you will not be able to use BoE initializers directly in class definition. The initializers are supplied at the point of static member definition in .cpp file.

This can be done much more compactly in C++17, but I'd guess that you are using Arduino IDE, which still sticks to C++11.

---

Also, make them const, if appropriate.

Looking at the documentation at IoT DevKit web site you linked I see that it contains a number of ridiculous typos making it almost unusable. It is quite possible that you will run into problems with their library if you properly use const-correctness in your code.