Quick Q: why there is no data-race in the following case?

By Adrien Hamelin | Feb 13, 2017 12:48 PM | Tags: intermediate

Quick A: No write is triggered so no data race occurs.

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why there is no data-race in the following case?

Data races are not static properties of your code. They are properties of the actual state of the program at execution time. So while that program could be in a state where the code would produce a data race, that's not the question.

The question is, given the state of the system, will the code cause a data race? And since the program is in a state such that neither thread will write to either variable, then the code will not cause a data race.

Data races aren't about what your code might do. It's about what they will do. Just as a function that takes a pointer isn't undefined behavior just because it uses the pointer without checking for NULL. It is only UB if someone passes a pointer that really is NULL.

Using QtCreator together with the Visual Studio Build Tools

By Meeting C++ | Feb 10, 2017 03:26 AM | Tags: tools qt boost basics

A first posting about working with Qt and Visual C++ in QtCreator

Using QtCreator together with the Visual Studio Build Tools

by Jens Weller

From the article:

For a while I've been using QtCreator as my IDE, mostly because its deep integration with Qt, as most of my projects are Qt related. With this, I also preferred (and still do a little) to use the MinGW builds of Qt on Windows. In the past, as GCC was a little bit better with the newer standards, today, well, never change a running system...

Dependencies in the Gang of Four examples -- Zebedee Mason

By zebedee | Feb 9, 2017 10:25 AM | Tags: None

Zebedee Mason discusses in his recent article some GOF idioms and analyzes them with his tool DeepsEnds.

Dependencies in the Gang of Four examples

by Zebedee Mason

From the article:

The example C++ code from the GoF (Gang of Four) book Design Patterns has had its dependencies analysed with DeepEnds. Certain examples have been refactored to remove circular dependencies enabled by pre-declaration of classes. These cycles in the graph serve to reduce the ability to subsequently modify the code with ease.

Fold Expressions--Rainer Grimm

By Adrien Hamelin | Feb 6, 2017 01:57 PM | Tags: intermediate experimental

Do you know how they work?

Fold Expressions

by Rainer Grimm

From the article:

With fold expressions you can implement the from Haskell known functions foldl, foldr, foldl1 and foldr1 directly in C++. These four functions successively reduce a list to a single value...

Wrapping Callbacks with Futures--Anthony Williams

By Adrien Hamelin | Feb 6, 2017 01:45 PM | Tags: intermediate c++11

Using futures with callbacks.

Wrapping Callbacks with Futures

by Anthony Williams

From the article:

Libraries the perform time-consuming operations, or network-based operations, often provide a means of running the task asynchronously, so that your code can continue with other things while this operation is performed in the background...

Un-Deprecate Your Qt Project--Giuseppe D'Angelo

By Marc Mutz | Feb 5, 2017 11:39 PM | Tags: None

Giuseppe D'Angelo explains how the Qt project deprecates APIs, a challenge every library project faces.

Un-Deprecate Your Qt Project

by Giuseppe D'Angelo

From the article:

Any product needs to evolve if it wants to remain competitive. If the development bandwidth is finite, from time to time there is the need to drop some ballast. This does not necessarily mean dropping working functionality and leaving users in the cold. At least in Qt most of the time this actually means replacing working functionality with better working functionality.

This process has being going on in Qt since forever, but since Qt 5.0 we’ve started to formalize it in terms of documentation hints and macros in the source code. This was done with a precise purpose: we wanted Qt users to discover if they were using deprecated APIs, and if so, let them know what better alternatives were available.

And since the very release of Qt 5.0.0 we’ve officially deprecated hundreds of APIs: a quick grep in QtBase alone reveals over 230 hits (mostly functions, but also entire classes).

C++ User Group Meetings in February

By Meeting C++ | Feb 1, 2017 10:28 AM | Tags: user group community

The monthly overview on upcoming C++ User Group Meetings:

C++ User Group meetings in February

by Jens Weller

From the article:

The monthly overview on upcoming C++ User Group meetings. For February there are already 33 User Group meetings planned. Also in this month are emBO++ and C++ Russia!

There are 4 new C++ User Groups: Nashua, NH, Vienna (Qt), Austin (Mentoring & Study Group), Montréal.

Stepanov-Regularity and Partially-Formed Objects vs. C++ Value Types -- Marc Mutz

By Giuseppe D'Angelo | Jan 30, 2017 04:43 AM | Tags: basics

Marc Mutz wrote in his recent article about the properties of default constructed object as required by Elements of Programming.

Stepanov-Regularity and Partially-Formed Objects vs. C++ Value Types

by Marc Mutz

From the article:

In this article, I will take a look at one of the fundamental concepts introduced in Alex Stepanov and Paul McJones’ seminal book “Elements of Programming” (EoP for short) — that of a (Semi-)Regular Type and Partially-Formed State.

Using these, I shall try to derive rules for C++ implementations of what are commonly called “value types”, focusing on the bare essentials, as I feel they have not been addressed in sufficient depth up to now: Special Member Functions.

zero-overhead C++17 currying & partial application -- Vittorio Romeo

By Vittorio Romeo | Jan 30, 2017 04:42 AM | Tags: c++17

This article briefly explains the concepts of "currying" and "partial application", then covers the design and C++17 implementation of a generic zero-overheader constexpr `curry` function.

zero-overhead C++17 currying & partial application

by Vittorio Romeo

From the article:

[...] many features introduced in the latest C++ standards allow functional patterns to thrive in your codebase, [...] like currying and partial application. [...] In this article we're going to:

* Introduce and briefly explain the two aforementioned concepts.

* Write a generic constexpr zero-overhead `curry` function in C++17.

* Analyze the generated assembly of the implementation to prove the lack of overhead.

[...]

Given a generic function object `f`, invoking `curry(f)` will return a curried/partially-applicable version of `f`. If `f` is constexpr-friendly, the returned one will be as well. `curry` should not introduce any overhead compared to hand-written currying/partial application.

Istream Idiosyncrasies -- Adi Shavit

By Adi | Jan 30, 2017 04:41 AM | Tags: None

Idiosyncrasies with istreams.

Istream Idiosyncrasies

by Adi Shavit

From the article:

A lot has been written and the vice and virtues of the C++ iostreams library.
While working on Argh, my little C++11 argument parsing library, I ran across some somewhat surprising idiosyncrasies and a few interesting lessons.