Home » Blog » Categories »

Quick Q: Why have move semantics? -- StackOverflow

By Blog Staff | Dec 3, 2013 04:42 AM | Tags: basics

Quick A: Because value semantics are clean and naturally (exception-)safe, and avoid the brittleness of pre-C++11 workarounds that resort to owning raw pointers.

As often happens, the question contains the answer...

Why have move semantics?

... Can't the client already take advantage of pointers to do everything move semantics gives us? If so, then what is the purpose of move semantics?

Move semantics:

std::string f()
{
    std::string s("some long string");
    return s;
}
int main()
{
    // super-fast pointer swap!
    std::string a = f();
    return 0;
}

Pointers:

std::string *f()
{
    std::string *s = new std::string("some long string");
    return s;
}

int main()
{
    // still super-fast pointer swap!
    std::string *a = f();
    delete a;
    return 0;
}

Dive into C++11 (#2) -- Frametime/FPS, constexpr, uniform initialization, and more

By Vittorio Romeo | Dec 3, 2013 03:59 AM | Tags: intermediate basics

Hello again, I’m Vittorio Romeo, a computer science student, hobbyist game developer and C++ enthusiast.

I've uploaded the second episode of "Dive into C++11" on my YouTube channel. You can find the first episode here.

You can find the complete playlist here.

In this episode we will learn more about two previously mentioned new awesome C++11 features: "constexpr" and "uniform initialization syntax".

Most importantly, we will also deal with a very big issue that every game developer must face: FPS/frametime, and how to avoid the game from behaving differently on slower/faster machines.

In addition, we'll also briefly learn about "const-correctness" and using the "noexcept" keyword.

We will analyze the "time-slice" method to allow the game to run smoothly and consistently on every machine.

In the last code segment, we will also "refactor" our code by creating a `Game` class, making our source much easier to read and maintain.

I greatly appreciate comments and criticism, and ideas for future videos/tutorials.

Feel free to fork the game's source code at: https://github.com/SuperV1234/Tutorials

Acquire and Release Fences Don't Work the Way You'd Expect -- Jeff Preshing

By hendrixjl | Dec 2, 2013 01:10 PM | Tags: advanced

The C++11 standard makes a distinction between acquire and release fences and acquire and release operations. The differences are important and can affect correctness as well as performance.

[Ed.: These correctness subtleties are another reason to avoid standalone fences... in addition to the notes in this article, there are performance reasons to do so, as mentioned in Sutter's linked talk. std::atomics are the correct tool in nearly all cases where in the past you'd have reached for a standalone fence.]

Acquire and Release Fences Don't Work the Way You'd Expect

by Jeff Preshing

From the article:

... It's perhaps surprising, then, that this definition does not apply to standalone acquire and release fences in C++11! Those are a whole other ball of wax.

To see what I mean, consider the following two code listings. They’re both taken from my post about the double-checked locking pattern in C++11. The code on the left performs a release operation directly on m_instance, while the code on the right uses a release fence instead. ...

CppQuiz.org officially launched -- Anders Schau Knatten

By Blog Staff | Dec 2, 2013 04:49 AM | Tags: intermediate

Anders Schau Knatten recently launched the new site CppQuiz.org inspired largely by Olve Maudal's C++ pub quizzes. So grab a refreshing beverage, pull up a chair, and try a few to start off the first week of December...

CppQuiz.org officially launched!

by Anders Schau Knatten

From the announcement:

What is it

CppQuiz.org is (as you might have guessed by now) an online C++ quiz. Each question is a full C++ program, and you are to figure out what its output is. I stole this format from Olve Maudal's pub quizzes, but with one major difference: While his quizzes are about what happens on his computer (which is very interesting for a more interactive format), CppQuiz.org asks about what the standard mandates the output to be. If the example code doesn’t compile, or has unspecified/undefined behaviour, you answer that.

The site will just keep throwing questions at you (training mode), optionally giving you a hint and finally give you a full explanation of the answer, with references to the C++11 standard. If you want, you can however start a new quiz (quiz mode), and get a fixed number of questions. At the end you get a score, and a link to give your friends to see if they can beat you. Neither mode requires you to register or log in.

How you can help

If you like the quiz and want to help, there are many ways to do so:

  • Create your own questions, as many have done
  • Help improve the design (pull requests, e-mail, Twitter)
  • Help improve the functionality (pull requests, e-mail, Twitter)
  • Any other feedback (comments to this post, e-mail, Twitter)

N3805: Spring 2014 JTC1/SC22/WG21 C++ Standardization Committee Meeting -- Peter Sommerlad

By Blog Staff | Nov 28, 2013 11:38 AM | Tags: None

A new WG21 paper is available. A copy is linked below, and the paper will also appear in the next normal WG21 mailing. If you are not a committee member, please use the comments section below or the std-proposals forum for public discussion.

Document number: N3805

Date: 2013-11-28

Spring 2014 JTC1/SC22/WG21 C++ Standardization Committee Meeting

by Peter Sommerlad

Excerpt:

C++ Standardization Committee Meeting

June 16th-21st 2014

The meeting will be held at the University of Applied Sciences, HSR Rapperswil, Switzerland

HSR Rapperswil and IFS Institute for Software invite you to the C++ Standards Committee Meeting at the picturesque shore of Lake Zurich...

Tips for founding new (C++) user groups -- Jens Weller

By Blog Staff | Nov 28, 2013 05:36 AM | Tags: None

We're seeing quite a few new C++ user groups being formed, and so it's a good time to link to this timely article by Jens Weller:

Founding local C++ User Groups

From the article:

Lets start into the discussion on founding user groups, there is in my opinion different approaches to get started, but I don't want this to be a discussion, so I'll just list what I think is right. First I think that a C++ User Group should be local, which means its usually for a certain region. From my expierence, people are willing to travel up to 70km one way to a user group meeting. So in order to get started, I think you'll need the following four points:

  • People
  • Location
  • Topics
  • Date

...

Quick Q: When do you need to declare a variable constexpr? -- StackOverflow

By Blog Staff | Nov 27, 2013 01:44 PM | Tags: intermediate

Quick A: When you want to use the variable in a way that requires its value to be known at compile time.

Here's a short nugget that helps demonstrate the meaning of constexpr:

Why is constexpr required even though member function is constexpr?

The following does not compile unless I put constexpr before initializer_list:

constexpr std::initializer_list<int> il = {
    1, 2, 3, 4, 5, 6, 7, 8, 9, 10
};
std::array<int, il.size()> a;

But initializer_list size is constexpr:

constexpr size_type size() const;

What are inline namespaces good for? -- StackOverflow

By Blog Staff | Nov 27, 2013 11:36 AM | Tags: intermediate

Quick A: For source-level library versioning.

A StackOverflow classic:

What are inline namespaces for?

C++11 allows inline namespaces, all members of which are also automatically in the enclosing namespace. I cannot think of any useful application of this -- can somebody please give a brief, succinct example of a situation where an inline namespace is needed and where it is the most idiomatic solution?

(Also, it is not clear to me what happens when a namespace is declared inline in one but not all declarations, which may live in different files. Isn't this begging for trouble?)