C++ language is constantly evolving, and for us, as for developers of a static analyzer, it is important to track all its changes, in order to support all new features of the language. In this review article, I would like to share with the reader the most interesting innovations introduced in C++17, and demonstrate them with examples.

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Now, developers of compilers are actively adding support for the new standard.

Fold expressions

I would like to start with a few words about what a fold is (also known as reduce or accumulate).
Fold is a function that applies the assigned combining function to sequential pairs of elements in a list, and returns a result. The simplest example is the summing up of elements in the list using a fold:

Example from C++:


std::vector<int> lst = { 1, 3, 5, 7 };
int res = std::accumulate(lst.begin(), lst.end(), 0,
[](int a, int b) { return a + b; });
std::cout << res << '\n'; // 16

If the combining function is applied to the first item in a list and to the result of the recursive processing of the tail of a list, then the fold is called 'right'. In our example, we will get:

1 + (3 + (5 + (7 + 0)))
If the combining function is applied to the result of the recursive processing at the top of the list (the entire list without the last element) and to the last element, then a folding is called 'left'. In our example, we will get:

(((0 + 1) + 3) + 5) + 7
Thus, the fold type determines the order of evaluation.

In C++17 there is also folding support for a template parameters list. It has the following syntax:
(pack op ...) A unary right associative fold
(... op pack) A unary left associative fold
(pack op ... op init) A binary right associative fold
(init op ... op pack) A binary left associative fold

op is one of the following binary operators:


+ - * / % ^ & | ~ = < > << >> += -= *= /= %=
^= &= |= <<= >>= == != <= >= && || , .* ->*

pack is an expression containing an undisclosed parameter pack

init - initial value

For example, here's a template function that takes a variable number of parameters and
calculates their sum:


// C++17
#include <iostream>

template<typename... Args>
auto Sum(Args... args)
{
return (args + ...);
}

int main()
{
std::cout << Sum(1, 2, 3, 4, 5) << '\n'; // 15
return 0;
}

Note: In this example, the Sum function could be also declared as constexpr.
If we want to specify an initial value, we can use binary fold:


// C++17
#include <iostream>

template<typename... Args>
auto Func(Args... args)
{
return (args + ... + 100);
}

int main()
{
std::cout << Func(1, 2, 3, 4, 5) << '\n'; //115
return 0;
}

Before C++17, to implement a similar function, you would have to explicitly specify the rules for recursion:


// C++14
#include <iostream>

auto Sum()
{
return 0;
}

template<typename Arg, typename... Args>
auto Sum(Arg first, Args... rest)
{
return first + Sum(rest...);
}

int main()
{
std::cout << Sum(1, 2, 3, 4); // 10
return 0;
}

It is worth highlighting the operator ',' (comma), which will expand the pack into a sequence of actions separated by commas. Example:


// C++17
#include <iostream>

template<typename T, typename... Args>
void PushToVector(std::vector<T>& v, Args&&... args)
{
(v.push_back(std::forward<Args>(args)), ...);

//This code is expanded into a sequence of expressions
//separated by commas as follows:
//v.push_back(std::forward<Args_1>(arg1)),
//v.push_back(std::forward<Args_2>(arg2)),
//....
}

int main()
{
std::vector<int> vct;
PushToVector(vct, 1, 4, 5, 8);
return 0;
}

Thus, folding greatly simplifies work with variadic templates.
Kate Milovidova 13 october 2017, 14:23

IT conferences and meetings on programming languages see a growing number of speakers talking about static code analysis. Although this field is quite specific, there is still a number of interesting discussions to be found here to help programmers understand the methods, ways of use, and specifics of static code analysis. In this article, we have collected a number of videos on static analysis whose easy style of presentation makes them useful and interesting to a wide audience of both skilled and novice programmers.

What is Static Analysis?
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Kate Milovidova 26 april 2017, 8:24

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In this article we'll look at the main features of SonarQube - a platform for continuous analysis and measurement of code quality, and we'll also discuss advantages of the methods for code quality evaluation based on the SonarQube metrics.

SonarQube is an open source platform, designed for continuous analysis and measurement of code quality. SonarQube provides the following capabilities:
Kate Milovidova 16 november 2016, 12:13

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One of the main problems with C++ is having a huge number of constructions whose behavior is undefined, or is just unexpected for a programmer. We often come across them when using our static analyzer on various projects. But, as we all know, the best thing is to detect errors at the compilation stage. Let's see which techniques in modern C++ help writing not only simple and clear code, but make it safer and more reliable.
What is Modern C++?

The term Modern C++ became very popular after the release of C++11. What does it mean? First of all, Modern C++ is a set of patterns and idioms that are designed to eliminate the downsides of good old "C with classes", that so many C++ programmers are used to, especially if they started programming in C. C++11 looks way more concise and understandable, which is very important.
Kate Milovidova 15 september 2016, 11:44

Nowadays a lot of projects are opening their source code and letting those who are interested in the development of it edit the code. OpenJDK is no exception, programmers PVS-Studio have found a lot of interesting errors that are worth paying attention to.

OpenJDK (Open Java Development Kit) - a project for the creation and implementation of Java (Java SE) platform, which is now free and open source. The project was started in 2006, by the Sun company. The project uses multiple languages- C, C++, and Java. We are interested in the source code written in C and C++. Let's take the 9th version of OpenJDK. The code of this implementation of Java platform is available at the Mercurial repository.

During verification, the analyzer found different errors in the project including: copy-paste, bugs in the operation precedence, errors in logical expressions and in pointer handling and other bugs, which are described in detail in this article.

It's always amusing to check a project which is used and maintained by a large number of people. The better and more accurate the code is, the more safely and effectively the program will work. Those bugs we found, are another proof of the usefulness of an analyzer, as it allows the detection of such errors which would otherwise be hard to detect doing simple code review.
Kate Milovidova 17 june 2016, 9:00

Here is a small e-Book for your attention: The Ultimate Question of Programming, Refactoring, and Everything. This book is intended for C/C++ programmers, but it could be of interest for developers using other languages as well.

What makes the book peculiar is the descriptions of real, not theoretical cases at the base of it. Each chapter starts with a code fragment taken from a real application, and then the author gives various tips of how this bug could be avoided. The questions touched upon in this book can help the readers improve the personal coding style and the coding standards used in the team.
Kate Milovidova 11 may 2016, 6:52

CppCat is a static code analyzer integrating into the Visual Studio 2010-2013 environment. The analyzer is designed for regular use and allows detecting a large number of various errors and typos in programs written in C and C++. For the purpose of popularizing it, we've decided to launch a student-support program granting free licenses to every higher school student who will contact and ask us about that. You just need to send us a photo of your student card or transcript.
Andrey2008 21 november 2014, 14:24



The authors of the PVS-Studio analyzer invite you to test your attentiveness.

Code analyzers never get tired and can find errors a human's eye cannot easily notice. We have picked a few code fragments with errors revealed by PVS-Studio, all the fragments taken from well-known open-source projects.

We invite you to take part in a competition against code analyzers to test your agility by trying to find the errors by yourself. You will be offered 15 randomly selected tasks. Every correct answer earns you one score if you give it within 60 seconds. The code fragments are short and 60 seconds is a fair limit.

Let's examine a couple of examples with errors for you to understand how to give the answer.

Andrey2008 18 september 2014, 16:15

OutsourcingAs you know, our main activity is development of the code analyzers PVS-Studio and CppCat. Although we have been doing this for a long time now and - as we believe - quite successfully, an unusual idea struck us recently. You see, we do not use our own tools in exactly the same way our customers do. Well, we analyze the code of PVS-Studio by PVS-Studio of course, but, honestly, the PVS-Studio project is far from large. Also, the manner of working with PVS-Studio's code is different from that of working with Chromium's or LLVM's code, for example.

We felt like putting ourselves in our customers' shoes to see how our tool is used in long-term projects. You see, project checks we regularly do and report about in our numerous articles are done just the way we would never want our analyzer to be used. Running the tool on a project once, fixing a bunch of bugs, and repeating it all again just one year later is totally incorrect. The routine of coding implies that the analyzer ought to be used regularly - daily.

OK, what's the purpose of all that talk? Our theoretical wishes about trying ourselves in third-party projects have coincided with practical opportunities we started to be offered not so long ago. Last year we decided to allocate a separate team in our company to take up - ugh! - outsourcing; that is, take part in third-party projects as a developer team. Moreover, we were interested in long-term and rather large projects, i.e. requiring not less than 2-3 developers and not less than 6 months of development. We had two goals to accomplish:
  • try an alternative kind of business (custom development as opposed to own product development);
  • see with our own eyes how PVS-Studio is used in long-term projects.
We have successfully solved both tasks. But this article is not about the outsourcing business; it is about our experience. We don't mean the organizational experience - there are plenty of articles about that. We mean the experience of working with the code of third-party projects. This is what we want to tell you about.
Andrey2008 23 june 2014, 6:52

Calculator
In this article I'm going to discuss a problem few people think of. Computer simulation of various processes becomes more and more widespread. This technology is wonderful because it allows us to save time and materials which would be otherwise spent on senseless chemical, biological, physical and other kinds of experiments. A computer simulation model of a wing section flow may help significantly reduce the number of prototypes to be tested in a real wind tunnel. Numerical experiments are given more and more trust nowadays. However, dazzled by the triumph of computer simulation, nobody notices the problem of software complexity growth behind it. People treat computer and computer programs just as a means to obtain necessary results. I'm worried that very few know and care about the fact that software size growth leads to a non-linear growth of the number of software bugs. It's dangerous to exploit a computer treating it just as a big calculator. So, that's what I think - I need to share this idea with other people.
Andrey2008 9 april 2014, 11:46
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