@programminginc - страница 1928

András

#cppbookguide

SjD

I think #cppbookguide will better in this case

there was a c++ link in the on the c page

SjD

so,thanks anyway

I_Interface

I think #cppbookguide will better in this case

Ye.

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klimi

A HA HA HA... totally haven't seen this 800x

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0xff

Md. Shahib

/get ide

Md. Shahib

/get best-book

Md. Shahib

/get best

Md. Shahib

/get cpp

Md. Shahib

/get cbook

Optimus

We can't create object for abstract class. Then what is the reason for using abstract class?

olli

We can't create object for abstract class. Then what is the reason for using abstract class?

To provide a common interface for different types (polymorphism)

I_Interface

We can't create object for abstract class. Then what is the reason for using abstract class?

U can create a pointer of this class.

Hami

Kitty memory?

Augmented

Hi friends, is this singleton approach correct? If not, where are the possible flaws?

Francisco

Hi friends, is this singleton approach correct? If not, where are the possible flaws?

I'd say that you should avoid sigletons, but yes, is correct. Maybe you can't access the instance pointer because it's private, but everything else should be okay. I don't know if the compiler generates more constructors, but you should check for copy, move, and assignments

Francisco

Just to be 100% sure you can't instanciate it

Francisco

Also, you may want to initialize the pointer inside the class, like static Singleton* instance = nullptr;

Augmented

Also, you may want to initialize the pointer inside the class, like static Singleton* instance = nullptr;

I was trying to do this in the header file

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error: non-const static data member must be initialized out of line

Augmented

Also, you may want to initialize the pointer inside the class, like static Singleton* instance = nullptr;

but in the cpp file, is okay to be 0 or nullptr

Francisco

I was trying to do this in the header file

I've just checked and it seems that you can't initialize a non-integral memeber inside the class, which is quite surprising for me. Also, maybe you prefer deleting the constructor rather than making them private

Francisco

I've just checked and it seems that you can't initialize a non-integral memeber inside the class, which is quite surprising for me. Also, maybe you prefer deleting the constructor rather than making them private

Okay, you can't, you need to initialize the class

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Okay, you can't, you need to initialize the class

Yes, is it good to use such basic singleton class implementation, as a parent for deriving different classes which must stay singleton?

Francisco

Yes, is it good to use such basic singleton class implementation, as a parent for deriving different classes which must stay singleton?

I personally wouldn't use singletons at all. But if you need it, I think you can do that

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Francisco

I guess you can, It's in the design patterns

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I personally wouldn't use singletons at all. But if you need it, I think you can do that

Thanks, I am writing a driver for CAN hardware, and software implementation of the CANOpen stack, for embeded system with no OS., There are limited number of peripherials I must handle, and I want to be sure, that it's memory leak free, and drivers can't be multiple times instantiated...

olli

Hi friends, is this singleton approach correct? If not, where are the possible flaws?

It's not thread safe

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It's not thread safe

How can be fixed? Anyway I am not using real-multitasking, but simple process forking with a lot of state machines... but I have hardware interrupts

olli

How can be fixed? Anyway I am not using real-multitasking, but simple process forking with a lot of state machines... but I have hardware interrupts

I'd just go with class Singleton { Singleton() = default; Singleton(const Singleton&) = delete; public: static Singleton& instance() { static Singleton instance_{}; return instance_; } }; assuming >= C++11

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I'd just go with class Singleton { Singleton() = default; Singleton(const Singleton&) = delete; public: static Singleton& instance() { static Singleton instance_{}; return instance_; } }; assuming >= C++11

Wow, it's quite clever... yes, i'm with C++17 now

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Is this lambda like?

olli

Is this lambda like?

no, but C++11 gauarantees thread-safe initialization of static varaibles in functions

Augmented

no, but C++11 gauarantees thread-safe initialization of static varaibles in functions

But it's reference, not pointer... i didn't know it's allowed that way

Augmented

no, but C++11 gauarantees thread-safe initialization of static varaibles in functions

Can i use an initialiser list in the private constructor declatration, or i must intialise variables else where?

olli

Can i use an initialiser list in the private constructor declatration, or i must intialise variables else where?

not sure i fully got what you meant, but sure you can use initializer lists in private constructors

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not sure i fully got what you meant, but sure you can use initializer lists in private constructors

Okay, thank you very much for the briliant idea, now i am experimenting with it, and seems to do the job... I can't test it now within a multitasking environment, but will try it with heavy loaded interrupts... I assume there isn't any possibility for memory leaks?