What is default access modifier by generated macro?

Development Programming & Scripting
1

Hello, forks.

I know cpp default class access modifier is private.

What I doubt is generated macro. I can access some functions which are not defined access modifier(so, I thought its private) in AGameMode such as StartMatch(), HasMatchStarted(), etc on its child class by Super keyword.

For example,

class CELLPORTAL_API ACellPortalGameMode : public AGameMode
{
    GENERATED_BODY()
    virtual void StartMatch();
    /* some code */
}

void ACellPortalGameMode::StartMatch()
{
	if (!HasMatchStarted())
	{
		// do something
	}
	Super::StartMatch();
}

However, I cannot access in below case. In this case, the compiler complaints for access violation error.

class CELLPORTAL_API ACCharacterBase : public ACharacter
{
    GENERATED_BODY()
    virtual void AccessTest() { /* code */  }
}

class CELLPORTAL_API ACCharacterJoe : public ACCharacterBase
{
	GENERATED_BODY()
	virtual void AccessTest() override { Super::AccessTest(); }
}

error C2248: ‘ACCharacterBase::AccessTest’ : cannot access private member declared in class ‘ACCharacterBase’

I tried to find what is difference, then I found out AGameMode includes GENERATED_UCLASS_BODY() macro at the first line, but others use GENERATED_BODY(). When I changed GENERATED_BODY() to GENERATED_UCLASS_BODY(), it complied (but occurred some link error for constructors).

So, I guess the auto generated macro would affect default access modifier, but I cannot go further. Does anyone have an idea about it?

2

Thanks! You cleared up my doubt.

3

Actually, GENERATED_BODY does not change the access modifier at all. So:

UCLASS()
class UThing : public UObject
{
public:
    GENERATED_BODY()

    void ThisIsPublic();
};

UCLASS()
class UThing : public UObject
{
private:
    GENERATED_BODY()

    void ThisIsPrivate();
};

The old GENERATED_UCLASS_BODY() used to change it to public in all cases.

However, I’ve just discovered that if you omit the specifier entirely then it makes everything following it public:

UCLASS()
class UThing : public UObject
{
    GENERATED_BODY()

    void ThisIsPublic();
};

This is a bug. I’ll investigate the feasibility of fixing it (it’s a trivial fix, but it might affect a lot of existing code).

Steve

4

Actually, it’s slightly worse than that, as the access is falling through from one class to the next. We’ll definitely get this fixed:

UCLASS()
class UThing1 : public UObject
{
public:
    GENERATED_BODY()

    void ThisIsPublic();
};

UCLASS()
class UThing2 : public UObject
{
    GENERATED_BODY()

    void ThisIsAlsoPublic();

private:
    void ThisIsPrivate();
};

UCLASS()
class UThing3 : public UObject
{
    GENERATED_BODY()

    void ThisIsAlsoPrivate();
};

Steve

////
the following is a message from Omnicypher:
speaking of privacy issues, i just gained the power to edit anyone’s posts for some reason… whether its a question or comment, it seems anything on the answerhub has an edit button for me. im not sure who i should report this too, but this is Omnicypher, editing Steve Robbs comment. I hope this isn’t a glitch where everyone can do this… I’m not sure how I should report this in a way that most people wont realize they have the power to edit anything… so i hope this message gets to the right person so this can be fixed.

5

Wow! What a quick support. Thanks a lot, Steve.

6

hi. please read your comment, it has some new information that might be helpful.

7

Don’t rely on the generated macro to provide access modifiers. Add them yourself.

You get your error because all class members are private by default.