June 16-21, Sofia, Bulgaria
By Blog Staff | Jul 15, 2013 04:18 AM | Tags: basics
Recently at Dr. Dobb's:
How the C++ Compiler Decides to Move Objects
by Andrew Koenig
From the article:
After reading this post, you should be able to figure out what
std::movedoes, although not necessarily how it does it...
By Blog Staff | Jul 13, 2013 04:59 PM | Tags: intermediate basics
C++14 is still very much a draft -- it only became feature-complete in April and is now in its primary comment ballot. But interest in this new standard is high, with a restarted "Guru of the Week" series focusing on C++14 and now Scott Meyers has produced the first book-like materials that include significant coverage of C++14.
C++11 Training Materials Updated -- Now With C++14 Info!
For the seventh time since originally releasing them over three years ago, I've updated my annotated training materials for "The New C++". Until this update, "the new C++" referred to C++11, but with this revision, I'm including treatment of several features from draft C++14 that I believe will make it into the new new standard. As far as I know, this makes my training materials the first "book-like" publication that covers features in C++14.
By Blog Staff | Jul 13, 2013 04:11 PM | Tags: intermediate
Inquiring minds want to know this classic question:
What is std::promise?
I'm fairly familiar with the new standard library's
std::thread,std::asyncandstd::futurecomponents (e.g. see this answer), which are straight-forward.However, I cannot quite grasp what
std::promiseis, what it does and in which situations it is best used. The standard document itself doesn't contain a whole lot of information beyond its class synopsis, and neither does just::thread.Could someone please give a brief, succinct example of a situation where an
std::promiseis needed and where it is the most idiomatic solution?
By Blog Staff | Jul 12, 2013 06:35 AM | Tags: intermediate
NoSenseEtAl asked:
Why noexcept is not enforced at compile time?
As you might know C++11 has noexcept keyword. Now ugly part about it is this:
Note that a noexcept specification on a function is not a compile-time check; it is merely a method for a programmer to inform the compiler whether or not a function should throw exceptions.
http://en.cppreference.com/w/cpp/language/noexcept_spec
So is this a design failure on the committee part or they just left it as an exercise for the compile writers
in a sense that decent compilers will enforce it, bad ones can still be compliant?
By Blog Staff | Jul 11, 2013 05:33 AM | Tags: intermediate
Readers ask:
What are “rvalue references for *this” for?
What are the most typical use cases of "rvalue references for
*this" which the standard also calls reference qualifiers for member functions?By the way, there is a really good explanation about this language feature here.
By stella | Jul 10, 2013 08:22 AM | Tags: basics
A new article on auto type deduction has been posted to IBM's C/C++ cafe.
C++11 new feature: auto type deduction
by FangLu
This article describes a new C++11 feature that deprecates the auto keyword as a storage class specifier, but reserves auto as a type specifier that directs the compiler to deduce the type of a declared variable from its initialization expression. This auto type deduction feature can increase programming convenience, eliminate potential typing errors, and simplify the code.
By Blog Staff | Jul 10, 2013 08:18 AM | Tags: optimization intermediate
The Visual C++ Team Blog has been publishing an article series about optimizations that C++ compilers perform for you under the covers to make your code more efficient. This short nugget answers a question people sometimes ask: "What's constant folding, and why do I care?"
Optimizing C++ Code: Constant-Folding
by Jim Hogg
From the article:
This post examines Constant-Folding -- one of the simplest optimizations performed by the VC++ compiler. In this optimization, the compiler works out the result of an expression while it is compiling (at “compile-time”), and inserts the answer directly into the generated code. This avoids the cost of performing those same calculations when the program runs (at “runtime”).
Here is an example...
By Blog Staff | Jul 9, 2013 03:39 PM | Tags: basics
Quick A: There isn't, because unique_ptr is unique. If you want shared ownership or shared observation, you need a shared_ptr. The "shared"-ness in shared_ptr enables both shared ownership (shared_ptr) and shared observation (weak_ptr).
shared_ptr<> is to weak_ptr<> as unique_ptr<> is to... what?
In C++11, you can use a
shared_ptr<>to establish an ownership relation with an object or variable andweak_ptr<>to safely reference that object in a non-owned way.You can also use
unique_ptr<>to establish an ownership relation with an object or variable. But what if other, non-owning objects want to also reference that object?weak_ptr<>isn't helpful in this case. Raw pointers are helpful but bring various downsides (e.g. they can be automatically initialized tonullptrbut this is accomplished through techniques that are not consistent with thestd::*_ptr<>types).What is the equivalent of
weak_ptr<>for non-owning references to objects owned viaunique_ptr<>?
By Blog Staff | Jul 9, 2013 09:57 AM | Tags: basics
A chapter worth reading on InformIT, excerpted from C++ Primer 5th Edition:
Working with Dynamic Memory in C++
by Stan Lippman, Josée Lajoie, Barbara Moo
C++ lets you allocate objects dynamically. The authors of C++ Primer discuss why properly freeing dynamic memory is a rich source of bugs, and how the new library defines smart pointers --
shared_ptr,unique_ptr, andweak_ptr --that make managing dynamic memory much safer.
By Blog Staff | Jul 9, 2013 09:13 AM | Tags: None
Quick A: Try vector<unique_ptr<base>> by default.
What's the preferred C++ idiom to own a collection of polymorphic objects?
... I'm sure there's something related to move semantics in there (I could move the objects passed to
add_items()to own them) but I still can't figure out how my collection would be declared.What is the C++ idiom for this sort of polymorphic ownership (particularly with STL containers)?