Category: San Diego C++ Meetup

Hello everyone,

I’ve been super busy at work hence the delay in this blog post that summarizes our 52nd San Diego C++ Meetup.

This time, we hosted a Qualcommer co-worker – Alex Reinking.

Alex is very knowledgeable in many fields and in specific, he likes build systems. We had an offline chat before he submitted the talk for the July session. We talked about CMake, FetchContent, Package managers and it was very clear to me that Alex would be great speaker in our meetup.

Here is the recording:

Alex started by taking us through the general idea of CMake as a build generator and also mentioned its popularity in the community.

Few important bullet points and take away:

1. Under the hood, Package managers do more that you realize. Like patching code and similar.
2. As a library, we would like to provide the users the best experience when using our library with CMake.
3. Alex has a very nice demo posted here: alexreinking/sdcppmu-diffuse. Building on Linux and MSVC with Emscripten targeting WebAssembly(Linux)/SDL(Windows).
4. Always use the latest CMake. This is something that I like in CLion which is usually bundled with the latest, or almost latest CMake.
5. CMake’s find_package() is the one true way to locate dependencies.
6. FetchContent is nice but it will clutter your CMake “env”, unless upstream project is written well enough.
7. Halide (see Alex’s Bio) has CMake helper functions like “add_halide_generator“, “add_halide_library“) – a generator that must run on the host system, even when cross compilation is involved.
8. Alex walks us through the path of getting your library “FetchContent” friendly for consumers.
9. Interesting discussion on Why we should not create 2 targets (shared and static for example).
10. Why not GLOB for sources.
11. Discussion on what to place and NOT to place in your CMakeLists.txt. For example – compile options – probably should go into Presets.
12. Other CMake related constructs that were new to me: ALIAS for add-Library, BASE_DIRS + target_sources, GenerateExportHeader, CMakeDependentOption, CMakePackageConfigHelpers, configure_package_config_file, write_basic_package_version_file.

More information can be found in the recording.

Thank you!

Kobi

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Abstract
In this talk, we will discuss the best practices as of the latest CMake version for writing C and C++ libraries that are easy for everyone to consume. We will build a toy application that demonstrates switching between static and shared library types, dependency management, creating accurate CMake config packages, and cross-compilation involving code generators. We will see how writing CMake lists that are minimal and declarative leads to more correct and maintainable builds.

Bio
Alex is a research scientist at Qualcomm Compiler Labs. He got his Ph.D. in Programming Languages from UC Berkeley in 2022. Since 2020, Alex has served as an open-source maintainer for Halide, a popular DSL for optimizing image and tensor processing; in this capacity, he has overhauled the build system, CI infrastructure, and the release process. Alex has contributed build system improvements to prominent open-source projects, including WABT, tinyxml2, and Herb Sutter’s cppfront, and has found and fixed large CMake bugs. His blog page: https://alexreinking.com

Link to the event

Hello all,

It was yet another exciting night this time hosting Ben Deane!

His talk named “Applicative – the Forgotten Functional Pattern“

Here is the recording:

Ben is a great speaker and he loves Functional programming

First – the Abstract:

Abstract

Monads get all the press. Functors are often presented as a prerequisite to monads. Applicative (functor) almost never gets mentioned. But it’s massively useful – to the point where a lot of the time when we think about a “monadic interface” what we really want is an applicative interface.
This talk will put applicative in the limelight, showing how it works and why it’s so powerful, with lots of examples grounded in code; there are no category theory diagrams in this talk. Attendees will come away with a solid understanding of the applicative pattern and its many uses. And as a byproduct, their opinions of monads will probably change too.
Optionals. Expected. Ranges. Futures. Parsing. Validation. Error Handling. Transforms. Functions themselves. These are all examples where thinking in terms of applicatives (and importantly, NOT just reaching for “a monadic interface”) helps us write simpler, more composable code. If you’re kind of fuzzy about functors and monads, what’s missing is probably the third piece of the puzzle: applicative.

Summary

I’d classify this talk as intermediate++. Ben mentioned many concepts like optional, ranges, Monads and std::expected just to name a few.

Throughout the talk, Ben presents Haskell syntax and C++. The Haskell part is easy to grok though if you are seeing this syntax for the first time, you might want to pause the recording and make sure you understand it since the sub-sequence slides will build on top of it. There are also some heavy generic programming slides that might need more attention when you go through the recording. No spoilers here on the conclusion and the take away (regarding Monads vs Applicative)

Overall I learned a ton from this talk and have some homework to go and explore more on this domain.

We have an incredible future ahead of us in terms of new syntax and new language and library capabilities.

I’d end with a meme

About BEN DEANE

Principal Software Engineer at Intel
Ben has been programming in C++ for this whole millennium. He spent just over 20 years in the games industry working for companies like EA and Blizzard; many of the games he worked on used to be fondly remembered but now he’s accepted that they are probably mostly forgotten. After getting more interested in modern C++, in the teens he started giving internal company talks and then talks at various conferences, spreading ideas about types, algorithms and declarative and functional techniques. In 2018 he left the games industry and worked in finance for a short spell, writing high-frequency trading platforms using the most modern C++ that compilers could support. Now he is a Principal Software Engineer at Intel where he puts monads inside your CPU.

Thank you!

Kobi

Summary of the last San Diego C++ Meetup – held on April 11 2023. This was our 49th meeting since inception on March 12 2019.

Sorry again for the delay posting this summary. I had some technical issues uploading the recording last week and finally found some time to write the summary.

Recording can be found here:

Discussion points:

C++Quiz.

Three fun C++Quiz questions. One related to UB when writing to const, another one related to copies made when using range for loop with auto and the last one was related to references and alias.

Walletfox slide – C++ Functional programming

I really love Walletfox (Ruzena Gurkaynak) work. The website has FP slides, Ranges-v3 booklet that can be purchased online (ebook + printed) which is highly recommended!

We discussed one slide related to Curring and “Partial” (like bind1st and similar but modern style).

Why I cannot emplace_back

This came up during code review. I was demonstrating the differences between vector::emplace_back of a simple struct vs unique_ptr<> “hosting” this struct. More info in the recording.

Using std::tie in C++

I love C++17 [structured, binding] but when I have no choice or when it falls short, I use std::tie. Also std::tie has other few applications that makes it easy to write code. I demonstrated few.

PImpl pattern

The final course was PImpl pattern. One of my favorite and a very useful pattern. We went through the definitions in cppreference, and mostly went over Herb’s GOTW #100/101.

That’s it for April meeting summary.

Thank you!

Kobi

Yet another apology on the delay in posting the summary of the latest San Diego C++ Meetup. Super busy at work.

It’s finally Friday night and I have some time to sit down and write the summary.

4 years. Total of 48 meeting. Missed just one session, March 2020 when COVID started. I was not ready yet for the whole virtual meeting thing and here we are today. 3 years later – all virtual.

The first year was in person, we were just building up the group in San Diego. XCOM-LABS were generous enough to provide the space, first in La Jolla UTC and then Miramar area – yeah, where you can find Top-Gun

For the past 3 years, Qualcomm is sponsoring (paying the meetup.com fees) this group, especially my VP, Charles B which is a big supporter.

For meeting #48, we had Amir Kirsh. This is not Amir’s first appearance in the group and we really like his talks.

You can find the meetup page here, the YouTube channel has many past recording including the latest one with Amir.

Talk abstracts:

C++ Incidental Explorations by Amir Kirsh
This talk will guide us through some interesting discussions of C++ using questions from StackOverflow for inspiration. With these questions as our starting point, we will try to learn C++, explore some of the corners of the language, get lost down a few rabbit holes, and become familiar with some topics usually reserved for “language lawyers”. We finish by exploring whether, and how, ChatGPT might help with writing C++ in the future.

Summary: This was a unique session. Exploring Stackoverflow C++ questions, discussing about various ways to analyze C++ questions, searching for unique questions and finally, we had a nice discussion on GPT, ChatGPT and how this can help us, especially in the context of programming and C++.

Among the many topics covered, we discussed Chrono library, auto as an optimization opportunity, overload resolution, const RValue – is it useful?, Iterator class, Reverse Iterator tricks, UB in accessing unwound stack address, — > “operator” , sorting, class owning a member of its own type and many more. All in just 90 minutes!

Amir’s Bio: Amir Kirsh is a Lecturer at the Academic College of Tel-Aviv-Yaffo and a Visiting Lecturer at Stony Brook University, as well as Developer Advocate at Incredibuild. Amir also serves as one of the organizers of the CoreCpp meetup group and CoreCpp conference in Tel-Aviv, as well as a member of the Israeli ISO C++ National Body.

Thank you Amir! and see you all next time!

Kobi

Apologize about the delay in posting this. Here are the minutes from the last San Diego C++ Meetup, held on Wed Feb 15 2023 5PM Pacific time. Thank you everyone for joining!

The meetup was recorded and uploaded to sdcppmu YouTube channel here:

So what did we have in this meeting?

First – I presented an interesting Req in Qualcomm ML/AI Cloud group. The req number is 3046377 and you can find it on Qualcomm jobs website.

Next, we went over 4 cppquiz questions. The idea here, besides fun, is to learn new elements and constructs in the language. The cppquiz questions were 333,312,318 and 319. We learned about post increment, struct/class inheritance and members visibility, operator void(), casting to void and finally, ternary operator with class inheritance and implicit conversion using implicit constructor.

Next, we discussed the following use case how-to-prevent-stdfunction-to-bool-conversion-in-c-function-overloading . We demonstrated usage of C++20 concepts (std::invocable) as well as enable_if_t.

The next topic is a very interesting one. Polymorphic arrays pitfalls. segmentation-fault-in-operator-delete . It talks about allocating an array of a derived class type and assigning it to a base class pointer. When we do pointer arithmetic, it’s all messed up, and obviously delete []p will also fail. A good picture of what’s going on can be found here:

We demonstrated few alternatives. For example, std::vector<p*> would be a good approach and instead would look like:

More info and details in the actual recording.

The last one was about template instantiation, RValue binding to const& vs non const& and the implications. Also mentioned (again) implicit conversion in the same context. The details can be found here: why-does-removing-const-from-the-constructor-parameter-stop-the-class-from-being-instantiated . The actual code is here:

Long story short, when you have const& the compiler can create temp of What<int> with the which is passed, so it tries to instantiate What<T>(The) and check if this Heck(const What<int>&) can be used . If there is no const, you cannot do such RValue/temp binding hence no need to instantiate What<T>. Though we did mention that Heck(The) constructor will be a better match anyway since it does not require any user defined conversion to happen.

That’s it for this #47 session of sdcppmu. See you next month with a special guest. Will be announced soon!

Hello everyone!

Tonight (Dec 6 2022) we hosted Amir Kirsh from Incredibuild.

Amir went over the various use cases of using std::move, also highlighting std::forward usage, various pitfalls and he provided us with good set of guidelines on when to use and not to use std::move.

Highly recommended!

Here is the recording (can be found in Youtube channel sdcppmu)

Our event link on meetup.com can found here: San Diego C++ Meetup

Today, Monday, November 14, we had our #44 San Diego C++ Meetup.

Unfortunately, there seem to have some issues in the posted link on meetup and many could not attend. Giant apology on this one. Not sure what happened and how but would pay extra attention next time (Dec 2022 here I come …).

Tonight, we discussed few interesting C++ Quiz questions, talked about RxCpp book from packt –

And also talked about Boost.Asio from the excellent Boost book:

here is the recording:

Enjoy!

Kobi