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Start speaking at Meeting C++ 2018

By Meeting C++ | Jun 6, 2018 07:19 AM | Tags: speaking meetingcpp community basics

As it was a big success last year, Meeting C++ has again a track for new speakers, and is looking for folks which like to submit their talk ideas to the conference!

The call for Talks for Meeting C++ 2018 ends on June 17th.

Call for a more diverse program at Meeting C++ 2018!

by Jens Weller

From the article:

Last years track for new speakers was a great success, so Meeting C++ will dedicate a track to this now in every year. So I'd like to reach out to the C++ Community, who do you think has something interesting to say about C++ and could start speaking at this years Meeting C++?

Using C++17 std::optional--Bartlomiej Filipek

By Adrien Hamelin | May 10, 2018 11:36 AM | Tags: basics

A reminder.

Using C++17 std::optional

by Bartlomiej Filipek

From the article:

Let’s take a pair of two types <YourType, bool> - what can you do with such composition?

In this article, I’ll describe std:optional - a new helper type added in C++17. It’s a wrapper for your type and a flag that indicates if the value is initialized or not. Let’s see where it can be useful and how you can use it.

Passing Booleans to an Interface in an Expressive Way--Jonathan Boccara

By Adrien Hamelin | May 8, 2018 12:29 PM | Tags: basics

Readability is important.

Passing Booleans to an Interface in an Expressive Way

by Jonathan Boccara

From the article:

In order to allow a function to behave in several different way, and to allow its caller to choose amongst these behaviours, we have several tools at our disposal. Plenty, actually.

There are various sorts of polymorphisms embedded in the language such as virtual functions and templates. And we’ve also seen that a caller can specify the desired behaviour explicitly at call site. We’ve seen how to accomplish this by using tag dispatching, and also how to choose between enums and tag dispatching depending on your need.

I now want to top it off with a really simple technique, that will cost you almost nothing, but one that will make your code much more expressive. And even if it’s not rocket science I’m sharing this with you today because I’ve seen many a piece of code that could have benefited from it...

Quick Q: What is a non-trivial constructor in C++?

By Adrien Hamelin | Mar 12, 2018 12:24 PM | Tags: basics

Quick A: All constructors that you define are not trivial.

Recently on SO:

What is a non-trivial constructor in C++?

In simple words a "trivial" special member function literally means a member function that does its job in a very straightforward manner. The "straightforward manner" means different thing for different kinds of special member functions.

For a default constructor and destructor being "trivial" means literally "do nothing at all". For copy-constructor and copy-assignment operator, being "trivial" means literally "be equivalent to simple raw memory copying" (like copy with memcpy).

If you define a constructor yourself, it is considered non-trivial, even if it doesn't do anything, so a trivial constructor must be implicitly defined by the compiler.

In order for a special member function to satisfy the above requirements, the class must have a very simplistic structure, it must not require any hidden initializations when an object is being created or destroyed, or any hidden additional internal manipulations when it is being copied.

For example, if class has virtual functions, it will require some extra hidden initializations when objects of this class are being created (initialize virtual method table and such), so the constructor for this class will not qualify as trivial.

For another example, if a class has virtual base classes, then each object of this class might contain hidden pointers that point to other parts of the very same object. Such a self-referential object cannot be copied by a simple raw memory copy routine (like memcpy). Extra manipulations will be necessary to properly re-initialize the hidden pointers in the copy. For this reason the copy constructor and copy-assignment operator for this class will not qualify as trivial.

For obvious reasons, this requirement is recursive: all subobjects of the class (bases and non-static members) must also have trivial constructors.

C++17: Initializers for if & switch statements--Marc Gregoire

By Adrien Hamelin | Jan 24, 2018 06:38 PM | Tags: c++17 basics

Small reminder:

C++17: Initializers for if & switch statements

by Marc Gregoire

From the article:

Two small, but very useful C++17 features are initializers for if and switch statements. These can be used to prevent polluting the enclosing scope with variables that should only be scoped to the if and switch statement. The for statement already supports such initializers since the beginning...