By Adrien Hamelin | Apr 14, 2017 01:07 AM | Tags: None
Quick A: Lambda captures are const by default, and it is not possible to move a const.
Recently on SO:
std::move with std::shared_ptr in lambda
The captured variable ptr in a lambda is by default const, i.e. the type of ptr is
const std::shared_ptr<int>.
std::movecannot move out const objects, so a copy is created instead.If you really want to move it, the ptr must be allowed to be mutable:
auto lambda = [ptr]() mutable {
By Adrien Hamelin | Apr 14, 2017 01:03 AM | Tags: community basics
Quick A: No
Recently on SO:
Are the experimental features of modern C++ reliable for long-term projects?
Is it guaranteed that all compliant compilers have the same experimental features?No, experimental features are optional.Are experimental features prone to big changes that make them unreliable?Yes, the C++ committee might even decide to abandon a feature or in the process of standardization a defect might come up that would force a feature to change.Generally, it's not a good idea to depend on experimental features. Experimental features are exactly what the word says (i.e., to experiment with).
By Adrien Hamelin | Apr 14, 2017 01:01 AM | Tags: community c++11
A new useful feature in Qt:
Disabling narrowing conversions in signal/slot connections
by Giuseppe D'Angelo
From the article:
A small new feature that I have added to Qt 5.8 is the possibility of disabling narrowing conversions in the new-style QObject::connect statement. In this short blog post I would like to share with you why I thought this was useful and therefore implemented it...
By Jason Turner | Apr 13, 2017 05:27 PM | Tags: None
Episode 58 of C++ Weekly.
Negative Cost Embedded C++ - Part 1
by Jason Turner
About the show:
Jason continues his series on embedded C++ with an example of how templates and constexpr can provide flexibility while reducing the compile size and increasing performance.
By Marco Arena | Apr 11, 2017 05:31 AM | Tags: visual studio
A quick tour of the Visual Studio native debugger and how it can help you in all areas of your C++ development:
C++ Debugging and Diagnostics
by Adam Welch
From the article:
Debugging is one of the cornerstones of software development, and it can consume a significant portion of a developer’s day. The Visual Studio native debugger provides a powerful and feature-rich experience for finding and fixing problems that arise in your applications...
By robwirving | Apr 7, 2017 12:17 PM | Tags: None
Episode 96 of CppCast the only podcast for C++ developers by C++ developers. In this episode Rob and Jason are joined by Sara Chipps to discuss Jewelbots, Arduino and getting girls interested in STEM fields.
CppCast Episode 96: Jewelbots with Sara Chipps
by Rob Irving and Jason Turner
About the interviewee:
Sara Chipps is a JavaScript developer based in NYC. She has been working on Software and the Open Source Community since 2001. She’s been obsessed with hardware and part of Nodebots since 2012.
She is the CEO of Jewelbots, a company dedicated towards drastically changing the number of girls entering STEM fields using hardware.
She was formerly the CTO of Flat Iron School, a school dedicated to teaching people of all ages how to build software and launch careers as software developers.
In 2010 she cofounded Girl Develop It, a non-profit focused on helping more women become software developers. Girl Develop It is in 45 cities, and has taught over 17,000 women how to build software.
By Adrien Hamelin | Apr 5, 2017 02:24 PM | Tags: c++11 advanced
An issue we do not think often about:
Post-Conditions on Self-Move
by Eric Niebler
From the article:
TL;DR: In addition to the usual rule about move operations leaving the source object in a valid but unspecified state, we can add an additional guideline (not quite a rule, but follow it anyway):
Self-move assignment should “work” and leave the object in a valid but unspecified state.
By Adrien Hamelin | Apr 5, 2017 02:15 PM | Tags: intermediate
Quick A: Make it impossible to construct a class of the wrong type.
Recently on SO:
Prevent user from derive from incorrect CRTP base
1) make all constructors of Base private (if there are no constructors, add one)
2) declare Derived template parameter as friend of Base
template <class Derived> class Base { private: Base(){}; // prevent undesirable inheritance making ctor private friend Derived; // allow inheritance for Derived public : void call () { static_cast<Derived *>(this)->call_impl(); } };After this it would be impossible to create any instances of the wrong inherited D2.
By Adrien Hamelin | Apr 3, 2017 01:42 PM | Tags: intermediate c++11
Quick A: use a std::unique_lock with std::try_to_lock parameter in the constructor.
Recently on SO:
Conditionally acquire an std::mutex
It is actually unsafe to have a unique_lock accessible from multiple threads at the same time. I'm not familiar with the opencv portion of your question, so this answer is focused on the mutex/lock usage.
static std::mutex s_FAST_GPU_mutex; { // Create a unique lock, attempting to acquire std::unique_lock<std::mutex> guard(s_FAST_GPU_mutex, std::try_to_lock); if (guard.owns_lock()) { cv::gpu::FAST_GPU(/*params*/)(/*parameters*/); guard.unlock(); // Or just let it go out of scope later } else { cv::FAST(/*parameters*/); } }This attempts to acquire the lock, if it succeeds, uses FAST_GPU, and then releases the lock. If the lock was already acquired, then goes down the second branch, invoking FAST
By Adrien Hamelin | Apr 3, 2017 01:36 PM | Tags: intermediate c++11
Do you use them badly?
Smelly std::pair and std::tuple
by Arne Mertz
From the article:
Depending on their use,
std::pairandstd::tuplecan be code smells. That’s why we should be careful around these two.Having a code smell is not a no-go, it’s more like a red flag. It’s one of those things that are not a problem themselves but rather a hint that there might be a less obvious problem hidden in the code.