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Quick Q: Regarding shared_ptr reference count block

By Adrien Hamelin | Nov 28, 2018 12:03 PM | Tags: intermediate community

Quick A: it is an implementation detail for the std.

Recently on SO:

Regarding shared_ptr reference count block

(1) Regarding size: How can I programatically find the exact size of the control block for a std::shared_ptr?

There is no way. It's not directly accessible.

(2) Regarding logic: Additionally, boost::shared_ptr mentions that they are completely lock-free with respect to changes in the control block.(Starting with Boost release 1.33.0, shared_ptr uses a lock-free implementation on most common platforms.) I don't think std::shared_ptr follows the same - is this planned for any future C++ version? Doesn't this also mean that boost::shared_ptr is a better idea for multithreaded cases?

Absolutely not. Lock-free implementations are not always better than implementations that use locks. Having an additional constraint, at best, doesn't make the implementation worse but it cannot possibly make the implementation better.

Consider two equally competent programmers each doing their best to implement shared_ptr. One must produce a lock-free implementation. The other is completely free to use their best judgment. There is simply no way the one that must produce a lock-free implementation can produce a better implementation all other things being equal. At best, a lock-free implementation is best and they'll both produce one. At worse, on this platform a lock-free implementation has huge disadvantages and one implementer must use one. Yuck.

Meeting C++ and Meeting Embedded trip report--Conan C/C++ Package Manager

By Adrien Hamelin | Nov 28, 2018 11:55 AM | Tags: community

Were you there? 

Meeting C++ and Meeting Embedded trip report

by Conan C/C++ Package Manager

From the article:

On Wednesday, before Meeting C++, we attended and presented a talk at Meeting Embedded, a new conference about many topics related to embedded systems. C++ and C had a relevant role in this conference, obviously (accordingly to Dan Saks statistics around 60% in embedded code is C, then around 20% is C++, followed by assembly), but where other topics presented, like Rust, protocols for embedded (MQTT), academic and professional education, real-time systems.

We did our own talk Continuous Integration of C/C++ for embedded and IoT with Jenkins, Docker and Conan, which went quite well, especially considering that we were running a real demo, live updating the embedded code in a Raspberry PI, that was built with Docker in Jenkins, using cross-compiled (from Windows) packages, and uploaded to Artifactory, all of that done in the live demo...

How to teach C++--Marius Elvert

By Adrien Hamelin | Nov 27, 2018 01:53 PM | Tags: community

Do you have a way?

How to teach C++

by Marius Elvert

From the article:

In the closing Keynote of this year’s Meeting C++, Nicolai Josuttis remarked how hard it can be to teach C++ with its ever expanding complexity. His example was teaching rookies about initialization in C++, i.e. whether to use assignment =, parens () or curly braces {}. He also asked for more application-level programmers to participate.

Well, I am an application programmer, and I also have experience with teaching C++. Last year I held a C++ introductory course for experienced C programmers who mostly had never used C++ before. From my experience, I can completely agree with what Nico had to say about teaching C++. The language and its subtlety can be truly overwhelming.

Most of the complexity in C++ boils down to tuning your code for optimal performance. We cannot just leave that out, can we? After all, the sole reason to use C++ is performance, right?

How to Design Function Parameters That Make Interfaces Easier to Use (1/3)--Jonathan Boccara

By Adrien Hamelin | Nov 26, 2018 02:30 PM | Tags: intermediate community

Readability is important.

How to Design Function Parameters That Make Interfaces Easier to Use (1/3)

by Jonathan Boccara

From the article:

When you look at an function in an interface, 3 prominent things give you indications about how to use it: its name, its parameters and its return type. And when you look at a piece of code calling that function, it’s just its name and its function parameters.

We’ve already covered in details how to give good names to the components of your code. Now we’re going to examine how to design function parameters in a way that both your interfaces and the code that calls them are as expressive as can be.

Summed up in one sentence, you want to make the decision of what arguments to pass to your functions a no-brainer.

There are a lot of things to say about how to achieve this. So much so that you will find the contents broken down into 3 articles in order to make it easier to digest:

  • Part 1: interface-level parameters, one-parameter functions, const parameters,
  • Part 2: calling contexts, strong types, parameters order,
  • Part 3: packing parameters, processes, levels of abstraction.

To support this series I’ve taken many examples from interfaces I’ve worked on, except that I’ve stripped out all domain aspects to make them both simpler and disclosable...

San Diego Committee Meeting: A Trip Report--Corentin Jabot

By Adrien Hamelin | Nov 19, 2018 01:08 PM | Tags: experimental community

Trip report.

San Diego Committee Meeting: A Trip Report

by Corentin Jabot

From the article:

As I left Rapperswil earlier this year, I said very firmly that I would not go to the San Diego Meeting.

Crossing an ocean to work on C++ 12 hours a day for a week is indeed madness.

And so naturally, I found myself in a San Diego hotel straight from the 60s, to do some C++ for a week. With the exception of the author of this blog, all people there are incredibly smart and energetic, and so a lot of great work was done...

Trip Report: Freestanding in San Diego--Ben Craig

By Adrien Hamelin | Nov 19, 2018 01:05 PM | Tags: experimental community

One more report.

Trip Report: Freestanding in San Diego

by Ben Craig

From the article:

All three are dealing with "freestanding". I've been working for the last year or so trying to redefine freestanding in a way that would be useful to more people. I have personal experience using C++ in various operating system kernels / drivers, and a bit of experience working on micro controllers and digital signal processors, so that's where my papers focused. At the CppCon 2018 SG14 meeting, some GPU companies have said that my definitions are useful for their architectures (with some tweaks), and I've heard from several other people that my definitions are even useful in some environments where performance and determinism are key, even when there is an OS. I'm still trying to figure out if and how to incorporate all these groups into one thing that could get standardized.

I pitched "Freestanding Proposal" at my first WG21 meeting was November of 2017 in Albuquerque. I was an unknown then. San Diego was my third WG21 meeting. All the papers and interviews and trip reports have now made it where people were asking me about freestanding quite frequently. There were a few times I got stopped while walking around by someone I had never talked to before, and they knew who I was, and asked about freestanding. I found this very flattering. I'm thrilled (and terrified) that my work is getting such visibility...

Use the official range-v3 with MSVC 2017 version 15.9--CoderCasey

By Adrien Hamelin | Nov 12, 2018 01:21 PM | Tags: experimental community

Everything is in the title.

Use the official range-v3 with MSVC 2017 version 15.9

by CoderCasey

From the article:

We’re happy to announce that the ongoing conformance work in the MSVC compiler has reached a new milestone: support for Eric Niebler’s range-v3 library. It’s no longer necessary to use the range-v3-vs2015 fork that was introduced for MSVC 2015 Update 3 support; true upstream range-v3 is now usable directly with MSVC 2017.

Using STL algorithms with cppcheck--Paul Fultz II

By Adrien Hamelin | Nov 7, 2018 11:31 AM | Tags: community

Making the code more expressive.

Using STL algorithms with cppcheck

by Paul Fultz II

From the article:

From Sean Parent’s C++ Seasoning talk, he explains how raw loops suffer from several issues:

  • Difficult to reason about and difficult to prove post conditions
  • Error prone and likely to fail under non-obvious conditions
  • Introduce non-obvious performance problems
  • Complicates reasoning about the surrounding code

Instead algorithms should be preferred, either using the algorithms in the standard library or writing a new algorithm. Even more so, Sean Parent suggests that all coding guildines should be replaceed with “No raw loops” in order to improve code quality...

Exploring Clang Tooling Part 3: Rewriting Code with clang-tidy--Stephen Kelly

By Adrien Hamelin | Nov 7, 2018 11:29 AM | Tags: community

The series continue.

Exploring Clang Tooling Part 3: Rewriting Code with clang-tidy

by Stephen Kelly

From the article:

In the previous post in this series, we used clang-query to examine the Abstract Syntax Tree of a simple source code file. Using clang-query, we can prototype an AST Matcher which we can use in a clang-tidy check to refactor code in bulk.

This time, we will complete the rewriting of the source code...