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A C error handling style that plays nice with C++ exceptions

By Stefanus Du Toit | May 4, 2014 07:52 AM | Tags: intermediate

If you've ever wondered why someone might throw an exception from a destructor, this article provides a legitimate example:

A C Error Handling Style that Plays Nice with C++ Exceptions

by Stefanus Du Toit

From the article:

By choosing a particular convention for a C API's error handling, we were able to very conveniently translate errors from the C API to C++ exceptions. ... Every experienced C++ programmer I know has opinions on how errors should be handled. I've found this style to be quite useful when layering C++ on top of C, and I think there's some beauty in the interplay between C and C++ here.

 

Quick Q: If I use shared_ptrs to own objects, must I use weak_ptrs to observe them? -- StackOverflow

By Blog Staff | May 2, 2014 07:57 AM | Tags: None

Quick A: No. Remember that weak_ptr and * are both valid non-owning pointers. Use * when you know the pointed-at object will outlive this pointer. Use weak_ptr when you don't know whether the pointed-at object will outlive this pointer, and the pointed-at object is owned by shared_ptrs.

For more good information, see the top answer to this question yesterday on SO:

Smart pointers + cycles + “->”

Sometimes I'm really sure that I want to have circular dependence of pointers, and every object on cycle should be able to use his pointer (so it can't be weak_ptr).

My question is: Does this mean that I have bad design?

What if I want to implement graph? Can I use smart pointers? In graphs there are cycles, but with weak_ptr I can't use "->". What can I do?

I read some articles, reference and topics on StackOverflow, but it looks like I still don't get smart pointers. Really, why doesn't exists some variant of weak_ptr with "->"?

Qt & JSON

By Meeting C++ | Apr 30, 2014 10:16 AM | Tags: qt basics

Recently I could play around with Qt5 JSON API:

Qt & JSON

by Jens Weller

From the Article:

With Qt5 there is a new API for reading and writing JSON files in Qt. In the last days I had the chance to play around with this API, as I implemented importing and exporting different data sets from and to JSON.

Quick Q: Are class member initializers evaluated at compile time? -- StackOverflow

By Blog Staff | Apr 30, 2014 03:34 AM | Tags: basics

Quick A: Maybe.

Recently on SO:

Does in class member initialization takes place at compile time or run-time?

In C++11 a new feature was introduced where the programmer can initialize class member variables inside class's definition, see code below:

struct foo
{
  int size = 3;
  int id   = 1;
  int type = 2;
  unsigned char data[3] = {'1', '2', '3'};
};

Is this initialization takes place during compile time or this feature is just syntactic sugar and member variables are initialized in the default constructor?

Nugget: Context-sensitive keywords -- Tony DaSilva

By Blog Staff | Apr 29, 2014 04:35 AM | Tags: basics

Recently on Bulldozer00:

Context Sensitive Keywords

by Tony DaSilva

From the article:

With the seriousness of keyword introduction in mind, one might wonder why the override and final keywords were added to C++11. Surely, they’re so common that millions of lines of C/C++ legacy code will get broken. D’oh!

But wait! To severely limit code-breakage, the override and final keywords are defined to be context sensitive...

Range Comprehensions -- Eric Niebler

By Blog Staff | Apr 28, 2014 11:38 AM | Tags: experimental advanced

Do you "comprehend" ranges? From a key participant in some of the latest discussion about ranges for C++:

Range Comprehensions

by Eric Niebler

From the article:

I’ve been busy since I last wrote about ranges. I have a lot of news to share, but in this post, I’m going to narrowly focus on a recent development that has me very excited. It’s a new feature that I’m calling range comprehensions, and they promise to greatly simplify the business of creating custom ranges...

noexcept: what for? -- Andrzej KrzemieĊ„ski

By Blog Staff | Apr 28, 2014 09:51 AM | Tags: intermediate

From the desk of Andrzej:

noexcept -- what for?

by Andrzej Krzemieński

From the article:

In this post I would like to share my observation on where using noexcept really adds value. It is less often than what one might expect, and it does not have that much to do with throwing or not throwing exceptions. The conclusion surprises me a bit, and I hesitate to present it because it is counter to the advice I hear from people I consider authorities on the subject...

Async-Await in C++ -- Paolo Severini

By Marco Arena | Apr 28, 2014 08:52 AM | Tags: intermediate experimental concurrency

severini-await.PNGParis, April 2014: Paolo Severini explores the Async-Await pattern and the related proposal for C++17, showing also an example by using Visual Studio 2013 November CTP.

Async-Await in C++

by Paolo Severini

From the article:

... what about native [C++] programming? Is there anything like async/await that we can use with our futures? We can find the answer in N3858, another proposal made by Gustafsson et al. for C++17.

This time the changes proposed are to the language itself and not just to the library. The idea is to introduce the equivalent of C# async methods in the form of resumable functions. They can be thought as the basis to add to C++ the support for real co-routines, and are not strictly related to the <future> library, even though they have being defined especially to improve the usability of futures and promises...