Variables not initialized in Class Constructor

Question

I'm creating a library driver for AdaFruit's GFX library. During Constructor initialization, all the variables (set in another .cpp) are returned as zero. This code has several modular files to separate graphics functions from graphics primitives from device interfacing. What am I doing wrong?

In the Arduino sketch I call the class constructor: MB_GFX_SPI (in file MB_GFX_SPI.cpp). In the Constructor I'm call a function: mbR.SetMatrixSize (in another file raster.cpp). Also in the Constructor I call a function: clearScreen (in the same file MB_GFX_SPI.cpp).

The test variable mbR.r_totNumChannels set in clearScreen is returned with 99. All the variables set in mbR.SetMatrixSize return zero.

//Test Sketch
//Initialize both the Adafruit library and the current library.
//Instantiate an object mbGFX so all Adafruit GFX and MB_GFX add-on functions are addressed as mbGFX.xxx(); 
MB_GFX_SPI mbGFX = MB_GFX_SPI(Period, numCathodeLeds, numAnodeLeds, CathodeSSPin, AnodeSSPin);
//In file MB_GFX_SPI.cpp
MB_GFX_SPI::MB_GFX_SPI(int Period, int numCathodeLEDS, int numAnodeLEDS,
 int CathodeSSPin, int AnodeSSPin) 
 : Adafruit_GFX(numCathodeLEDS, numAnodeLEDS) {
 mbR.SetMatrixSize(numCathodeLEDS, numAnodeLEDS);
 clearScreen(0);
}
void MB_GFX_SPI::clearScreen(uint16_t color) {
 mbR.r_totNumChannels = 99; //test set value
}
//In file mb_raster.cpp
void mbRasterClass::SetMatrixSize(int numCathodeLeds, int numAnodeLeds){
//cathodes require 1 byte per channel
//anodes require 1 bit per channel
 int numAnodeChannels = numAnodeLeds;
 int numCathodeChannels = mbX.pin2pin * numCathodeLeds; //times 1 or 3 
 r_numCathodeRegisters = (int)((numCathodeChannels+7)/8); //select next higher number of registers
 r_numCathodes = 8 * r_numCathodeRegisters; //must be whole 8 bit registers - is every single chatode pin
 r_numAnodeRegisters = (numAnodeChannels+7)/8; //round up to next register number
 r_numAnodes = 8 * r_numAnodeRegisters; //must be whole 8 bit registers
 r_PWMBufferSize = r_totNumChannels = r_numAnodes * r_numCathodes;
 r_PWMBuffer = (uint8_t *) realloc(r_PWMBuffer, r_totNumChannels); //resize array for PWMBuffer
}

• BrettFolkins: can you give a function that shows what isn't working in code? something you would expect to do one thing, but isn't working out that way? I'm not certain I know what you mean by "the variables return zero". Also some more information about the members of an MB_GFX_SPI, and where mbR comes from.
• Edgar Bonet: Try initializing mbGFX with its regular constructor (GFX_SPI mbGFX(...);) instead of using copy-initialization (GFX_SPI mbGFX = MB_GFX_SPI(...);).

Answer 1

First, I would do what Edgar Bonet suggested, call the normal constructor:

MB_GFX_SPI mbGFX (Period, numCathodeLeds, numAnodeLeds, CathodeSSPin, AnodeSSPin);

Second, I'm not keen on what you are doing in the constructor for a variable which appears to be at global scope (mbGFX).

See What's the "static initialization order fiasco"?

Basically you cannot assume that constructors in different compilation units are called in any defined sequence, you also cannot assume that the system has been initialized yet (ie. init() called).

Thus, things that address the hardware (eg. clearScreen(0);) may not work properly, or at all.

• user3511552: thanks for additional suggestions. I've recently installed Visual Studio+Visual Micro and have been tracing the initialization process.