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Universal References in C++11 -- Scott Meyers

By Blog Staff | Oct 9, 2012 11:32 AM | Tags: intermediate advanced

Recorded live at C++ and Beyond 2012:

Universal References in C++11

Scott Meyers

Given that rvalue references are declared using "&&", it seems reasonable to assume that the presence of "&&" in a type declaration indicates an rvalue reference. That is not the case...

In this article, I describe the two meanings of "&&" in type declarations, explain how to tell them apart, and introduce new terminology that makes it possible to unambiguously communicate which meaning of "&&" is intended. Distinguishing the different meanings is important, because if you think "rvalue reference" whenever you see "&&" in a type declaration, you'll misread a lot of C++11 code...

Poll: Portland attendees and subgroups

By Herb Sutter | Oct 7, 2012 02:44 PM | Tags: None

If you are planning to attend the Portland meeting, please fill out this brief poll to help us allocate rooms and plan for the week. Thanks!

 

 

Using Strings in C++ Template Metaprograms -- Abel Sinkovics and Dave Abrahams

By Blog Staff | Oct 2, 2012 02:07 PM | Tags: advanced

Fresh off the press at C++ Next:

Using strings in C++ template metaprograms

by Abel Sinkovics and Dave Abrahams

Of all the reasons to love metaprogramming, probably the most compelling is that it lets us embed “little languages” in our programs... Instead of C++ expressions, of course, strings could be used to represent the DSL code snippet in the embedding C++ code. In fact, that’s an approach used by many “traditional” libraries:

auto all_caps = std::regex("[A-Z]+"); // OK

The only problem is, the contents of that string are only known at runtime, which means the language has to be interpreted at runtime, and we lose the benefit of being able to translate the structure into compiled code. The “delayed evaluation” has been delayed too long.

If, however, these strings could be parsed at compile-time, the resulting programs could have optimal performance again...

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Unifying Generic Functions and Function Objects -- Dave Abrahams

By Blog Staff | Sep 26, 2012 03:53 AM | Tags: experimental advanced

From Dave Abrahams:

Unifying Generic Functions and Function Objects

I just got finished collaborating on a proposal with Faisal Vali and Herb Sutter to include generic lambdas and pythy functions in the core language. After the upcoming Portland committee meeting, we should have a good sense of how much appetite there is on the committee for including these features in C++.

While we were writing that paper, we got some of our most helpful comments and insights from Mathias Gaunard. It was a pivotal moment when Mathias reminded us that we could create operator overload sets explicitly with inheritance and using declarations, and then used it to demonstrate "overloaded lambda expressions..."

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Padding and Rearranging Structure Members -- Dan Saks

By Blog Staff | Sep 20, 2012 02:17 PM | Tags: intermediate

Hot of the press at Dr. Dobb's:

Padding and Rearranging Structure Members

By Dan Saks

... Multibyte objects often have an alignment ... a "requirement that objects of a particular type be located on storage boundaries with addresses that are particular multiples of a byte address". The Standard leaves it up to each target processor to specify its alignment requirements. That is, a processor might require that a 4-byte integer or pointer referenced as a single object be word aligned — at an address that's a multiple of four. A processor also might require that an 8-byte floating-point number be word aligned, or maybe even double-word aligned — at an address that's a multiple of eight.

According to the C Standard, a program that attempts to access an improperly aligned object produces undefined behavior. This means that the program is in error, but the exact consequences of that error are platform-dependent. With many processors, an instruction that attempts to access improperly aligned data issues a trap. With other processors, an instruction that accesses misaligned data executes properly but uses up more cycles to fetch the data than if the data were properly aligned...

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Casablanca: C++ on Azure -- John Azariah and Mahesh Krishnan

By Blog Staff | Sep 19, 2012 02:55 PM | Tags: None

Casablanca is a Microsoft incubation effort to support cloud-based client-server communication in native code using a modern asynchronous C++ API design. Think of it as Node.js, but using C++ -- from simple services, to JSON and REST, to Azure storage and deployment, and more.

Casablanca gives you the power to use existing native C++ libraries and code to do awesome things on the cloud server. In this talk from TechEd Australia, John Azariah and Mahesh Krishnan show how it's done.

Reminder: Bjarne Stroustrup live tomorrow in Austin, TX

By Blog Staff | Sep 18, 2012 10:45 AM | Tags: None

Reminder: Bjarne Stroustrup is appearing live tomorrow in Austin, TX.

C++11 Style: A Touch of Class (Bjarne Stroustrup)

September 19, Austin, TX, USA

What principles, techniques, and idioms can we exploit to make it easier to produce quality code? This presentation reflects my thoughts on what “Modern C++” should mean in the 2010s: a language for programming based on light-weight abstraction with a direct and efficient mapping to hardware, suitable for infrastructure code. I will make an argument for type-rich interfaces, compact data structures, integrated resource management and error handling, and highly-structured algorithmic code. I will illustrate my ideas and motivate my guidelines with a few idiomatic code examples. I will use C++11 freely. Examples include auto, general constant expressions, uniform initialization, type aliases, type safe threading, and user-defined literals. C++ features are only just starting to appear in production compilers, so some of my suggestions have the nature of conjecture. However, developing a “modern style” is essential if we don’t want to maintain newly-written 1970s and 1980s style code in 2020.