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C *

General-purpose, imperative computer programming language, supporting structured programming, lexical variable scope and recursion, while a static type system prevents many unintended operations

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Kernel Queue: The Complete Guide On The Most Essential Technology For High-Performance I/O

High performance *System Programming *C *Development for Linux *
Tutorial

When talking about high-performance software we probably think of server software (such as nginx) which processes millions requests from thousands clients in parallel. Surely, what makes server software work so fast is high-end CPU running with huge amount of memory and a very fast network link. But even then, the software must utilize these hardware resources at maximum efficiency level, otherwise it will end up wasting the most of the valuable CPU power for unnecessary kernel-user context switching or while waiting for slow I/O operations to complete.

Thankfully, the Operating Systems have a solution to this problem, and it's called kernel event queue. Server software and OS kernel use this mechanism together to achieve minimum latency and maximum scalability (when serving a very large number of clients in parallel). In this article we are going to talk about FreeBSD, macOS and kqueue, Linux and epoll, Windows and I/O Completion Ports. They all have their similarities and differences which we're going to discuss here. The goal of this article is for you to understand the whole mechanism behind kernel queues and to understand how to work with each API.

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Total votes 7: ↑7 and ↓0 +7
Views 1.2K
Comments 1

PVS-Studio checks the code of Flipper Zero dolphin

PVS-Studio corporate blog Open source *C++ *C *Programming microcontrollers *

Flipper Zero + PVS-Studio


Flipper Zero is an open-source multi-tool for geeks and penetration testers. It so happened that the Flipper Zero project and the PVS-Studio analyzer crossed paths. A philosophical question: should we check the project, if the project developers have already started fixing errors? Let's try to do this.

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Total votes 6: ↑5 and ↓1 +4
Views 564
Comments 0

Even small projects have bugs, or how PVS-Studio checked Blend2D

PVS-Studio corporate blog Open source *C++ *C *

We often check large projects because it's easier to find bugs there. What if we try PVS-Studio on a small project? In this article we analyze Blend2D — a library for vector 2D graphics. Let's look at what we found.


0894_Blend2d/image1.png


Introduction


It's no secret that large projects have fascinating errors. It's not just "the larger the codebase is – the more errors we can find". It's also a known fact that the density of errors grows along with the codebase. That's why we love checking large projects — to treat you with a variety of "yummy" and tricky errors and typos. Besides, it's always interesting to search through a huge project with lots of dependencies, legacy code, and other stuff.


Today I'm moving away from this tradition. I decided to take a small project and see what PVS-Studio can find there. I chose Blend2D — branch master, commit c484790.

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Total votes 3: ↑2 and ↓1 +1
Views 402
Comments 0

MISRA C: struggle for code quality and security

PVS-Studio corporate blog C++ *IT Standards *C *Programming microcontrollers *

A couple of years ago the PVS-Studio analyzer got its first diagnostic rules to check program code compliance with the MISRA C and MISRA C++ standards. We collected feedback and saw that our clients were interested in using the analyzer to check their projects for MISRA compliance. So, we decided to further develop the analyzer in this direction. The article covers the MISRA C/C++ standard and the MISRA Compliance report. It also shows what we already managed to do and what we plan to achieve by the end of the year.


0866_MISRA_C/image1.png

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Why do you need the MISRA Compliance report and how to generate one in PVS-Studio?

PVS-Studio corporate blog Information Security *C++ *C *Programming microcontrollers *

If you are strongly interested in MISRA and would like to understand whether your project meets one of the MISRA association's standards, there is a solution. It's name is MISRA Compliance. PVS-Studio has recently learned how to generate the MISRA Compliance report. This article describes how you can use this feature. This can make somebody's life better.

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Rating 0
Views 404
Comments 3

Linux kernel turns 30: congratulations from PVS-Studio

PVS-Studio corporate blog Open source *C++ *C *Development for Linux *

On August 25th, 2021, the Linux kernel celebrated its 30th anniversary. Since then, it's changed a lot. We changed too. Nowadays, the Linux kernel is a huge project used by millions. We checked the kernel 5 years ago. So, we can't miss this event and want to look at the code of this epic project again.

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Total votes 2: ↑2 and ↓0 +2
Views 1.3K
Comments 0

Static analysis protects your code from time bombs

PVS-Studio corporate blog C *

0848_Timebomb/image2.png
Static code analysis allows you to identify and eliminate many defects at an early stage. Moreover, it's possible to detect dormant errors that don't show themselves when they appear. They can cause many problems in the future and it requires many hours of debugging to detect them. Let's look at an example of such a dormant error.

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Total votes 2: ↑2 and ↓0 +2
Views 727
Comments 0

A Beautiful Error in the Implementation of the String Concatenation Function

PVS-Studio corporate blog C *

We, the PVS-Studio static code analyzer developers, have a peculiar view on beauty. On the beauty of bugs. We like to find grace in errors, examine them, try to guess how they appeared. Today we have an interesting case when the concepts of length and size got mixed up in the code.


0845_LFortran_strcat/image2.png

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Total votes 2: ↑1 and ↓1 0
Views 993
Comments 0

The Implementation of a Custom Domain Name Server by Using С Sockets

*nix *DNS *C *SQLite *
Sandbox

We describe the implementation of a custom Domain Name System (DNS) by using C socket programming for network communication, together with SQLite3 database for the storage of Internet Protocol (IP) for Uniform Resource Locator (URL). Then we provide a performance analysis of our implementation. Our code is available publicly [1].

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Total votes 5: ↑4 and ↓1 +3
Views 794
Comments 0

Example of How New Diagnostics Appear in PVS-Studio

PVS-Studio corporate blog Information Security *Perfect code *C++ *C *

PVS-Studio new C++ rule


Users sometimes ask how new diagnostics appear in the PVS-Studio static analyzer. We answer that we draw inspiration from a variety of sources: books, coding standards, our own mistakes, our users' emails, and others. Recently we came up with an interesting idea of a new diagnostic. Today we decided to tell the story of how it happened.

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Short-lived Music or MuseScore Code Analysis

PVS-Studio corporate blog Open source *C++ *C *Sound

Having only programming background, it is impossible to develop software in some areas. Take the difficulties of medical software development as an example. The same is with music software, which will be discussed in this article. Here you need an advice of subject matter experts. However, it's more expensive for software development. That is why developers sometimes save on code quality. The example of the MuseScore project check, described in the article, will show the importance of code quality expertise. Hopefully, programming and musical humor will brighten up the technical text.

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Total votes 2: ↑1 and ↓1 0
Views 528
Comments 0

PVS-Studio, Blender: Series of Notes on Advantages of Regular Static Analysis of Code

PVS-Studio corporate blog Information Security *Open source *C++ *C *

PVS-Studio and Blender


In our articles, we regularly repeat an important idea: a static analyzer should be used regularly. This helps detect and cheaply fix many errors at the earliest stage. It looks nice in theory. As we know, actions still speak louder than words. Let's look at some recent bugs in new code of the Blender project.

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