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Quick Q: Why assigning a value is calling the implicit constructor?

By Adrien Hamelin | May 24, 2016 12:30 PM | Tags: basics

Quick A: Because the default assignement operator knows only the type of your object, which it can get be calling the constructor.

Recently on SO:

What is the point of calling constructor with implicit conversion instead of assignment operator after an object is initalized?

There is no implicit CBox::operator=(double), so box = 2.0; has to create a temporary CBox object. It's equivalent to box = CBox(2.0);.

Making your constructor explicit disallows the implicit conversion from double to CBox, so no appropriate assignment operator exists, and you get a compile error.

Quick Q: Why is there no to_string(const string&)?

By Adrien Hamelin | May 24, 2016 12:26 PM | Tags: basics

Quick A: If you need such a function you can create it.

Recently on SO:

Why is there no to_string(const string&)?

You can just write your own templated function with proper overloads as follows:

#include <iostream>
#include <string>
using namespace std;

template<typename T>
std::string toString(const T& t) {
    return std::to_string(t);
}

std::string toString(const char* t) {
    return t;
}

std::string toString(const std::string& t) {
    return t;
}

int main() {
    cout << toString(10) << endl;
    cout << toString(1.5) << endl;
    cout << toString("char*") << endl;
    cout << toString(std::string("string")) << endl;
    return 0;
}

Quick Q: Being smart with smart pointers: avoiding shared_ptr overuse

By Adrien Hamelin | May 23, 2016 12:24 PM | Tags: intermediate c++11

Quick A: Use unique_ptr when you can.

Recently on SO:

Being smart with smart pointers: avoiding shared_ptr overuse

To allow unique_ptr/shared_ptr, you may use template:

// Dispatcher for make_unique/make_shared
template <template <typename...> class Ptr, typename T>
struct make_helper;

template <typename T>
struct make_helper<std::unique_ptr, T>
{
    template <typename ...Ts>
    std::unique_ptr<T> operator() (Ts&&... args) const {
        return std::make_unique<T>(std::forward<Ts>(args)...);
    }
};

template <typename T>
struct make_helper<std::shared_ptr, T>
{
    template <typename ...Ts>
    std::shared_ptr<T> operator() (Ts&&... args) const {
        return std::make_shared<T>(std::forward<Ts>(args)...);
    }
};

template <template <typename...> class Ptr, typename T, typename ... Ts>
auto make(Ts&&... args)
{
    return make_helper<Ptr, T>{}(std::forward<Ts>(args)...);
}

And then

bool get_resource_parameters(Param1& param1,..., ParamN& paramN)
{
    //...
}

template <template <typename...> class Ptr>
Ptr<resource> open_resource(...)
{
   Param1 param1;
   ...
   ParamN paramN;
   if(!get_resource_parameters(param1, ..., paramN))
       return nullptr;

   return = make<Ptr, resource>(param1, ..., paramN);
}

And check for nullptr instead of split bool and smart_pointer.

RAII versus Exceptions--Arne Mertz

By Adrien Hamelin | May 23, 2016 12:21 PM | Tags: intermediate efficiency

There is no fight, is there?

RAII versus Exceptions

by Arne Mertz

From the article:

Recently I received a question on Twitter whether to prefer RAII over Exceptions. I have seen similar questions being asked again and again over time, so there seems to be some need for clarification...

CppCon 2015 C++ Metaprogramming: A Paradigm Shift--Louis Dionne

By Adrien Hamelin | May 23, 2016 12:17 PM | Tags: intermediate efficiency

Have you registered for CppCon 2016 in September? Don’t delay – Early Bird registration is open now.

While we wait for this year’s event, we’re featuring videos of some of the 100+ talks from CppCon 2015 for you to enjoy. Here is today’s feature:

C++ Metaprogramming: A Paradigm Shift

by Louis Dionne

(watch on YouTube) (watch on Channel 9)

Summary of the talk:

Most people think metaprogramming is hard. It isn't; we just didn't have the right tools for it. This talk will present a new way of metaprogramming using the same syntax as that of normal C++. It will show how the runtime and the compile-time boundaries can be crossed almost seamlessly. It will show how compilation times can be reduced without sacrificing expressiveness. It will introduce Hana [1], a newly accepted Boost library using cutting edge features of the language in a creative way to solve the problem of metaprogramming for good.

James McNellis' talks @Italian C++ Conference 2016

By Marco Arena | May 23, 2016 12:09 AM | Tags: community

The talks James McNellis gave at the Italian C++ Conference 2016 are now online:

An Introduction to C++ Coroutines

One of the most interesting new features being proposed for C++ standardization is coroutines, formerly known as “resumable functions.”  C++ coroutines are designed to be highly scalable, highly efficient (no overhead), and highly extensible, while still interacting seamlessly with the rest of the C++ language.

This session will consist of an in-depth introduction to C++ coroutines.  We will begin by looking at the rationale for adding coroutines to the C++ language and then look at several examples that show [1] how to write a coroutine, [2] how to use the extensibility model to adapt existing libraries to work with C++ coroutines, and [3] how coroutines really work “under the hood,” using the Visual C++ implementation as a reference.  Finally, we will look briefly at the status of the C++ coroutines proposal and some of the competing ideas.

Slides

 

Adventures in a Legacy Codebase

Three years ago, the Visual C++ team undertook a project to substantially modernize and redesign the Microsoft C Runtime (CRT) with the goals of improving long-term maintainability, performance, and usability.  This work culminated with the release of the Universal CRT with Windows 10 and Visual Studio 2015.

In this session, I will discuss our team’s experiences from this project.  We’ll look at some of the techniques we used in modernizing a decades-old codebase and look at some of the challenges that we faced, lessons that we learned, and best practices that we developed during the course of the project.

Slides

An Overview of Static Analyzers for C/C++ Code--Aleksandr Alekseev

By Adrien Hamelin | May 20, 2016 02:42 PM | Tags: community

Which static tools do you use?

An Overview of Static Analyzers for C/C++ Code

by Aleksandr Alekseev

From the article:

C and C++ programmers tend to make mistakes when writing code.

Many of these mistakes can be found using -Wall, asserts, tests, meticulous code review, IDE warnings, building with different compilers for different operating systems running on different hardware configurations, and the like. But even all these means combined often fail to reveal all the bugs. Static code analysis helps improve the situation a little. In this post, we will take a look at some static analysis tools. [The author of this article is not an employee of our company, and his opinion may be different from ours.]...