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C++ quiz by PVS-Studio and Sergei Kushnirenko

By Andrey Karpov | Jan 8, 2024 09:56 AM | Tags: undefined behavio quiz memset memcmp iterators errors copy-paste

The PVS-Studio team along with Sergei Kushnirenko prepared a quiz based on his publications about errors he found. Take the quiz, challenge your focus and coding skills while looking for errors in the C++ code. Attention! When taking the quiz, you may exclaim that some tasks are unfair. Indeed. However, please relax and approach them with humor. The quiz is just for fun.

C++ quiz by PVS-Studio and Sergei Kushnirenko

by Sergei Kushnirenko

About the quiz:

After taking the quiz, you may have questions about why this or that answer is marked as correct or incorrect. Welcome to the article: "Breaking down the C++ quiz by Sergei Kushnirenko" — here you will find answers to your questions.  Please read it only after you have puzzled over code snippets with errors and undefined behavior. Be sure — it will be more interesting.

When an Empty Destructor is Required -- Andreas Fertig

By Blog Staff | Jan 2, 2024 04:46 AM | Tags: None

me.pngIn my previous post, "Why you shouldn't provide an empty destructor," we discussed the importance of not providing an empty destructor in most cases. However, in this post, we'll explore a rare exception to this rule that arises when using the PImpl idiom to hide implementation details, specifically in situations where the unique_ptr encounters issues with incomplete types. Let's delve into this exception and learn when it's necessary to provide an empty destructor.

When an Empty Destructor is Required

by Andreas Fertig

From the article:

As you probably know from life, not only programming. There is no rule without an exception. Let's talk about the one case that requires an empty destructor (yes, I know it sounds silly). Suppose you have the following code:

In file included from <source>:2:
In file included from /opt/compiler-explorer/gcc-12.2.0/lib/gcc/x86_64-linux-gnu/12.2.0/../../../../include/c++/12.2.0/memory:76:
/opt/compiler-explorer/gcc-12.2.0/lib/gcc/x86_64-linux-gnu/12.2.0/../../../../include/c++/12.2.0/bits/unique_ptr.h:93:16: error: invalid application of 'sizeof' to an incomplete type 'Orange'
        static_assert(sizeof(_Tp)>0,
                      ^~~~~~~~~~~
/opt/compiler-explorer/gcc-12.2.0/lib/gcc/x86_64-linux-gnu/12.2.0/../../../../include/c++/12.2.0/bits/unique_ptr.h:396:4: note: in instantiation of member function 'std::default_delete<Orange>::operator()' requested here
          get_deleter()(std::move(__ptr));
          ^
<source>:4:7: note: in instantiation of member function 'std::unique_ptr<Orange>::~unique_ptr' requested here
class Apple
      ^
<source>:6:27: note: forward declaration of 'Orange'
    std::unique_ptr<class Orange> mOrange{};
                          ^
1 error generated.
Compiler returned: 1
 
Essentially, this message tells you that the std::unique_ptr cannot instantiate the required destructor for itself typed with Orange. The simple reason is that, at this point, Orange has no visible destructor. Which is the entire point of the PImpl idiom. What now?

Releasing the keynotes of Meeting C++ 2023

By Meeting C++ | Dec 30, 2023 03:38 AM | Tags: performance meetingcpp intermediate community c++20 c++17 c++14 basics advanced

Highlighting the current video releases for Meeting C++ 2023: the keynotes

With this year Meeting C++ had a unique set of keynotes, covering 6 impossible problems for software devs with the opening keynote by Kevlin Henney, followed by great wisdom about how open communities thrive by Lydia Pintscher. The closing keynote by Ivan Čukić was an impressive medley composing various idioms with Prog(ressive) C++.

All these keynotes are worth watching, a great contribution to our knowledge base as a community. Thanks to Kevlin Henney, Lydia Pintscher and Ivan Čukić for preparing these great presentations!

Boost 1.84.0 has been released

By Blog Staff | Dec 28, 2023 01:26 PM | Tags: None

space.pngspace.pnggetboost.pngRelease 1.84.0 of the Boost C++ Libraries is now available.

These open-source libraries work well with the C++ Standard Library, and are usable across a broad spectrum of applications. The Boost license encourages both commercial and non-commercial use.

Release 1.84.0 contains two new libraries and numerous enhancements and bug fixes for existing libraries.

New Libraries

  • Cobalt: Basic algorithms and types for C++20 coroutines, from Klemens Morgenstern.
  • Redis: Redis async client library built on top of Boost.Asio, from Marcelo Zimbres Silva.

Here are some useful links for 1.84.0.


Marshall Clow and Glen Fernandes managed this release - we very much appreciate their continued hard work!

C++20, Spans, Threads and Fun -- Bartlomiej Filipek

By Blog Staff | Dec 27, 2023 04:28 PM | Tags: None

C++20_Spans_Threads_and_Fun.pngIn this post, we’ll have fun using C++20’s spans to process data on multiple threads. What’s more, we’ll be equipped with the latest concurrency features from C++20.

C++20, Spans, Threads and Fun

by Bartlomiej Filipek

From the article:

Our task is relatively simple but can be extended to various multi-phase computations.

We need to initialize a container with numbers, filter them, then build a histogram.

Here’s the overview of the process:

CLion Nova Explodes onto the C and C++ Development Scene -- Anastasia Kazakova

By Blog Staff | Dec 22, 2023 04:28 PM | Tags: None

clionnova.pngWe’re announcing a free early preview of CLion, which uses the ReSharper C++/Rider C++ language engine instead of the CLion "legacy" engine. The Preview build is available via our dedicated Toolbox App feed. At some point in 2024, depending on the results of the feedback collected, CLion Nova will be merged into CLion. Until then, the Preview build will be free to use and can be installed in parallel with your usual CLion (Classic) installation.

CLion Nova Explodes onto the C and C++ Development Scene

by Anastasia Kazakova

From the article:

The first C++ engine by JetBrains was designed for AppCode, our IDE for iOS and macOS developers. It was part of the IntelliJ Platform, initially written in Java and later also in Kotlin. The approach and the architecture of the engine serve many languages in IntelliJ-based IDEs well; however, this design turned out not to be the best fit for the C++ language specifically.

To more quickly align with the evolution of C++ and to separate the engine and IDE processes, a clangd-based engine was later added to CLion. Built on our custom branch of clangd, this engine detects any warnings and errors, shows them in the editor, and suggests quick-fixes, as well as performing highlighting, completion, and certain navigation actions. It’s also used for things like data flow analysis and MISRA checks. Meanwhile, CLion’s “legacy” engine is responsible for other code insight features like refactorings. You can see a detailed “list of responsibilities” in our CLion documentation.

Top 10 errors in C and C++ projects in 2023

By Andrey Karpov | Dec 22, 2023 05:26 AM | Tags: pvs-studio

New Year is coming! It means, according to tradition, it's time to recall 10 of the most interesting bugs that PVS-Studio found during 2023.

Top 10 errors in C and C++ projects in 2023

by Alexey Gorshkov

From the article:

In this case, the developers wanted to fill the keyEventList array with zeros. Pay attention to the third parameter — the number of bytes the developers wanted to fill with zeros. In this case, sizeof(keyEventList) evaluates the pointer size instead of the array size. It depends on the target platform, but most often it's 4 or 8 bytes. However, the size of the structure is clearly larger than 4 or 8 bytes.