Imported classes to render.cpp interfering with each other

RyanGo

Hi, I'm not very experienced with C++ and I've been trying to figure out what this bug is.

I'm trying to make my code as modular as possible so I've put several classes in .h and .cpp files. One of them is a Note object which for now just outputs a filtered square wave when its "process" is called. I've tested that this object works so far, but when I try to initialize another custom object to test, my Note object no longer outputs the square wave, only 0. I've gone as far as creating an entirely separate Dummy class with its own header and cpp file, which does nothing and is only initialized in setup.

The only other thing I've found is that if the Dummy class doesn't have any object variables, the Note outputs a square wave as expected, but as soon as I put a single object variable in the .h file, the Note's square wave stops working. If the Dummy class has functions and a constructor that's also fine, but for some reason, object variables are a problem. It doesn't matter if the variable is private or public. Once again this Dummy class is not at all related to the Note class other than them both being included in render.cpp, declared before setup, and constructed within setup. The Dummy class/object isn't called anywhere else.

I've never encountered anything like this and am absolutely flummoxed. Next thing I'm going to try is taking the other class's functionality out of a class and just store them as functions.

Here is an example of the Dummy .h and .cpp files

/***** dummy.h *****/
#ifndef DUMMY_H
#define DUMMY_H

class Dummy
{
public:
	Dummy();
private:
	// int testVar_;
};

#endif

#include "dummy.h"

Dummy::Dummy()
{
	// testVar_ = 0;
}

giuliomoro

it seems like you may have some uninitialised memory in the rest of your code. The size of the object of type Dummy will change whether it has an instance variable or not (in fact it may be of size 0 if it has none? That'd be funny). So look at your Note class and make sure all your instance variables are initialised appropriately. Or post more code here if you need more help.

RyanGo

I think that might have been it. I found one of my variables (my audio frame counter, which is very important to my square wave) was uninitialized. Now that I've initialized it, it seems to be working independent of other objects having instance variables, and in fact I'm actually having trouble recreating the bug with the old conditions.

Thanks a bunch! Tough lesson to learn the importance of always initializing variables :,)

giuliomoro

Great. It may be hard to keep track of what variables get initialised if you have multiple constructor. I normally use one of two approaches (or a combination of the two) to minimise code duplication, and depending on the variable types:

have all constructors do nothing except call a setup() or init() method, where the actual initialisation happens
place the initial value in the class declaration itself. e.g.:

class Dummy
{
public:
	Dummy();
private:
	int testVar_ = 0;
	int testVar1_ = 1;
	int testVar2_ = 2;
	int testVar3_ = 3;
};

this way you can immediately see what has not been initialised.

PS: instead of the #ifndef-based include guards (e.g.:

#ifndef DUMMY_H
#define DUMMY_H
...
#endif

it is safer (i.e.: no risk of typos or namespace conflicts) and simpler to just use

#pragma once

at the top of your header file.