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Modules update video available -- Doug Gregor

By Blog Staff | Dec 5, 2012 12:43 PM | Tags: experimental advanced

MP4 video of Doug Gregor's talk on Modules is now available via llvm.org. Combining links here:

Modules (MP4 video) (PDF slides)

Doug Gregor - Apple

The C preprocessor has long been a source of problems for programmers and tools alike.

Programmers must contend with widespread macro pollution and #include-ordering problems due to ill-behaved headers. Developers habitually employ various preprocessor workarounds, such as LONG_MACRO_PREFIXES, #include guards, and the occasional #undef of a library macro to mitigate these problems.

Tools, on the other hand, must cope with the inherent scalability problems associated with parsing the same headers repeatedly, because each different preprocessing context could effect how a header is interpreted – even though the programmer rarely wants it.

Modules seeks to solve this problem by isolating the interface of a particular library and compiling it (once) into an efficient, serialized representation that can be efficiently imported whenever that library is used, improving both the programmer’s experience and the scalability of the compilation process.

 

C++11 tempts OSS: KDevelop 4.6 IDE, KDE Frameworks 5, Qt 5.0 (Phoronix)

By Blog Staff | Dec 4, 2012 05:17 PM | Tags: None

HT to Michael Larabel and Phoronix: It's great to see more projects moving to adopt modern C++11, from C++98/03 and even from C. Here are three fairly well-known projects in the "thinking about" stage of taking the plunge.

More Open-Source Projects Eyeing Up C++11

by Michael Larabel

KDE developers are currently contemplating the idea of allowing a subset of the C++11 language to be used within the KDevelop code-base. This C++11 change would happen for the KDevelop 4.6 integrated development environment release. Reasons are shared in this article for why one should consider using C++11 code.

[...]

Qt 5.0 is taking advantage of C++11 too, but there it's being handled in a backwards compatible manner so the code will still build as C++03 on older compilers. There is also more Qt C++11 developer information shared via slides from the recent Qt Developer Days event.

KDE Frameworks 5 may also use C++11.

Continue reading...

Tour of C++: Second chapter posted

By Bjarne Stroustrup | Dec 2, 2012 10:25 PM | Tags: basics

This 2nd chapter of my Tour of C++ introduces the basic C++ abstraction mechanisms. If you have a 1990s view of C++, you are in for a few surprises: the integrated set of abstraction mechanisms in C++11 allows for simpler and more powerful abstractions than previously. For starters, pointers basically disappear from sight (hiding inside resource handles). Naturally, this is achieved without loss of performance. Enjoy!

Constructive comments would be most welcome.

Compile Time Computations -- Andrzej KrzemieĊ„ski

By Blair Davidson | Nov 30, 2012 02:38 PM | Tags: advanced

[Ed.: This is an old post but we feel it has valuable information about constexpr.]

This is a good article about constant expressions and computations at compile time. It gives good coverage of the new constexpr keyword for allowing compile-time and run-time evalution. constexpr is discussed rigorously with information on the rules required by the facility.

Compile-Time Computations

by Andrzej Krzemieński

[...] But now, consider the following example:

const int i = 2;

const char array[ i == 2 ? 64 : throw exception() ];

Throwing an exception (which is an expression) cannot be evaluated at compile-time, but since i == 2 is true, the third argument of conditional operator should not be evaluated; at least at run-time. So is the above a valid code? Not in C++03. It is valid however in C++11. Does this sound incredible? [...]

 

Continue reading...

 

Applied Informatics C++ Libraries and Tools Release 2012.1 now available

By Blog Staff | Nov 30, 2012 12:21 PM | Tags: None

Release 2012.1 of Applied Informatics C++ Libraries and Tools is now available.

These libraries extend the POCO C++ Libraries with additional features, including:

  • Remoting for RPC/IPC and SOAP/WSDL web services, including SOAP 1.1 and 1.2
  • Open Service Platform for building modular, extensible applications
  • DNSSD/Zeroconf
  • Universal Plug and Play (UPnP)
  • Fast Infoset processing
  • Secure remote access to smart devices.

New in release 2012.1 are:

  • Support for C++ code generation from XML Schema and WSDL documents
  • Allowing Remoting to invoke SOAP 1.1/1.2 web services created using other middleware technologies such as Java JAX-WS or Microsoft .NET WCF
  • New Remoting featuers to support MTOM, HTTP Basic and Digest authentication and HTTP compression (gzip content encoding), as well as remote events with the new TCP transport

A free evaluation version is available for download.

Exception-Safe Coding in C++ -- Jon Kalb

By Blair Davidson | Nov 30, 2012 10:04 AM | Tags: intermediate

Jon Kalb from the C++ Now 2012 conference.

Exception-Safe Coding in C++

by Jon Kalb

Are you 100% confident that your code is exception-safe?

Safe usage of exceptions is a non-trivial problem that the industry has struggled with for the better part of two decades. If you have fear, uncertainty, or doubt about exception safety or just want to see the best practices for using exceptions in C++, this session is for you. We'll start with "What is the problem we are trying to solve?" and discuss alternatives, acknowledge the challenges associated with with exception usage, and cover some well-meaning but misguided attempts at safety. I will then present a set of guidelines that are the basis for safe exception usage and solid implementation techniques, including how to transition from an exception-unsafe legacy code base.

When we are finished you will know how to produce code that is easier to write, easier to understand, faster, and 100% robust in the face of exceptions.

This is a two part video series. Links:

Enjoy!

Learn How to Capture by Move -- Marco Arena

By Marco Arena | Nov 30, 2012 08:05 AM | Tags: advanced

[Ed.: C++11 lambdas support capturing local variables by value and by reference... but not by move. This will likely be addressed in the next standard, but in the meantime we need workarounds, usually involving a shared_ptr, to get the right behavior. In this article, Marco Arena looks at the shared_ptr approach and offers another potential helper. Observing the tradeoffs in these workarounds can instructive.]

Learn How to Capture by Move

by Marco Arena

what if I want to capture by moving an object instead of both copying and referencing? Consider this plausible scenario:

function<void()> CreateLambda()

{

    vector<HugeObject> hugeObj;

    // ...preparation of hugeObj...


    auto toReturn = [hugeObj] { ...operate on hugeObj... };

    return toReturn;

}

This fragment of code prepares a vector of HugeObject (e.g. expensive to copy) and returns a lambda which uses this vector (the vector is captured by copy because it goes out of scope when the lambda is returned). Can we do better?

"Yes, of course we can!" – I heard. "We can use a shared_ptr to reference-count the vector and avoid copying it."  ...

Continue reading...

C++ Benchmark: std::vector vs. std::list -- Baptiste Wicht

By Baptiste Wicht | Nov 27, 2012 10:04 AM | Tags: intermediate

[Ed.: Another reason why vector is the default (not only, but preferred) standard container.]

C++ Benchmark: std::vector vs. std::list

by Baptiste Wicht

In C++, two of the most used data structures are std::vector and std::list. In this article, their performance is compared in practice on several different workloads.

It is generally said that a list should be used when random insert and remove will be performed (performed in O(1) versus O(n) for a vector). If we look only at the complexity, search in both data structures should be roughly equivalent, complexity being in O(n). When random insert/replace operations are performed on a vector, all the subsequent data needs to be moved and so each element will be copied. That is why the size of the data type is an important factor when comparing those two data structures.

However, in practice, there is a huge difference, the usage of the memory caches. All the data in a vector is contiguous where the std::list allocates separately memory for each element. How does that change the results in practice ?

This article shows the difference in performance between these two data structures. 

Continue reading...

Modules: Update on work in progress -- Doug Gregor

By Blog Staff | Nov 26, 2012 11:56 AM | Tags: experimental

[Updated to add video link]

Earlier this month, Doug Gregor gave a presentation on Modules at the November 2012 LLVM Developers' Meeting. Doug is lead Clang developer at Apple, chairs the WG21 Study Group on Modules (SG2), and in this talk reports his design goals and partial progress to date on designing and implementing a module system for C++. This talk is an extended version of the presentation Doug made at the Feb 2012 ISO C++ meeting in Kona.

The talk slides and video recording is available via the 2012 DevMeeting page.

Standardization note: SG2 was formed in February and has been relatively quiet as a handful of experts (notably Doug with Clang) make further progress on proof-of-concept designs and implementations. As this prototyping work coalesces, SG2 is expected to become active early in the new year.

Modules (MP4 video) (PDF slides)

Doug Gregor -- Apple

The C preprocessor has long been a source of problems for programmers and tools alike.

Programmers must contend with widespread macro pollution and #include-ordering problems due to ill-behaved headers. Developers habitually employ various preprocessor workarounds, such as LONG_MACRO_PREFIXES, #include guards, and the occasional #undef of a library macro to mitigate these problems.

Tools, on the other hand, must cope with the inherent scalability problems associated with parsing the same headers repeatedly, because each different preprocessing context could effect how a header is interpreted -- even though the programmer rarely wants it.

Modules seeks to solve this problem by isolating the interface of a particular library and compiling it (once) into an efficient, serialized representation that can be efficiently imported whenever that library is used, improving both the programmer's experience and the scalability of the compilation process.

Continue reading...