October 25, Pavia, Italy
November 6-8, Berlin, Germany
November 3-8, Kona, HI, USA
By Jens Maurer | May 25, 2023 06:46 AM | Tags: c++17 basics
An introduction to std::string_view
Modern C++ In-Depth — Is string_view Worth It?
by Michael Kristofik
From the article:
std::string_viewmakes it easier to write generic code that can accept read-only references to character sequences, regardless of the underlying container that holds that data. ... However, like normal references, there is potential for misuse.
By Blog Staff | May 24, 2023 08:09 AM | Tags: None
C language was defined to cover a large range of computer architectures, including many which would be considered museum relics today. It therefore takes a very conservative view of what is permitted, so that it remains possible to write C programs for those ancient systems. (Which weren’t quite so ancient at the time.)
How To Check If A Pointer Is In A Range Of Memory
by Raymond Chen
From the article:
Suppose you have a range of memory described by two variables, say,
byte* regionStart; size_t regionSize;And suppose you want to check whether a pointers lies within that region. You might be tempted to write
if (p >= regionStart && p < regionStart + regionSize)but is this actually guaranteed according to the standard?
By Blog Staff | May 22, 2023 03:03 PM | Tags: None
C++17 added a new compile time constant std:: which tells you (basically) the size of a cache line. The purpose of this is to allow you to lay out your structures in a way that avoids false sharing.
Why is
std::hardware_destructive_interference_sizea Compile-time Constant Instead of a Run-time Value?by Raymond Chen
From the article:
C++17 added a new compile time constant
std::which tells you (basically) the size of a cache line. The purpose of this is to allow you to lay out your structures in a way that avoids false sharing.¹hardware_ destructive_ interference_ size But how does the compiler know what the cache line size will be of the CPU the program will eventually be run on? Shouldn’t this be a run-time value instead of a compile-time value?
Well yes, the actual size of the cache line isn’t know until run-time, because it is only then that the program meets a CPU. But really, you want this to be a ...
By Blog Staff | May 19, 2023 02:58 PM | Tags: None
Event-driven applications, such as GUIs or servers, often apply the architecture pattern Reactor. A Reactor can accept multiple requests simultaneously and distribute them to different handlers.
Reactor
by Rainer Grimm
From the article:
The Reactor Pattern is an event-driven framework to concurrently demultiplex and dispatch service requests to various service providers. The requests are processed synchronously.
Problem
A server should
- be extendable to support new or improved services
- be performant, stable, and scalable
- answer several client requests simultaneously
The application should be hidden from multi-threading and synchronization challenges
Solution
- Each supported service is encapsulated in a handler
- The handlers are registered within the Reactor
- The Reactor uses an event demultiplexer to wait synchronously on all incoming events
- When the Reactor is notified, it dispatches the service request to the specific handler
By Blog Staff | May 17, 2023 09:43 AM | Tags: None
Last time I showed a couple of questions about initialization. Try them here if you haven’t already. In this article, I’ll show you the answers and add more notes about initialization in C++.
Q&A - C++ Initialization
by Bartlomiej Filipek
From the article:
Will this code work in C++11?
struct User { std::string name = "unknown"; unsigned age { 0 }; };
User u { "John", 101 };
- Yes, the code compiles in C++11 mode.
- The code compiles starting with C++14 mode.
- The code doesn’t compile even in C++20.
By Blog Staff | May 15, 2023 12:39 PM | Tags: None
During the construction of an XML file when you write an element, it is obvious that the last thing that you do is to write the closing tag. By obvious we mean: writing it down adds no new information (there is no other possible final instruction for this task), and it would be a bug if this instruction wasn’t there.
The Obvious Final Step
by Andrzej Krzemieński
From the article:
The title may be misleading, as I had to invent a new short term for the pattern that occurs in the code once in a while. Example first:
// write an element of an XML file xml.begin_element("port"); xml.attribute("name", name); xml.attribute("location", loc); xml.end_element("port"); // <-- the obvious final step
By Blog Staff | May 12, 2023 02:28 PM | Tags: None
In a previous blog post, Daniel Lemire showed how you could define ‘an interface’ in C++ using concepts and stated that he did not take into account inheritance as a strategy. He does so here.
Defining Interfaces in C++: Concepts Versus Inheritance
by Daniel Lemire
From the article:
In a previous blog post, I showed how you could define ‘an interface’ in C++ using concepts. For example, I can specify that a type should have the methods has_next, next and reset:
template <typename T>
concept is_iterable = requires(T v) {
{ v.has_next() } -> std::convertible_to<bool>;
{ v.next() } -> std::same_as<uint32_t>;
{ v.reset() };
};
By Giovanni Dicanio | May 11, 2023 11:10 AM | Tags: None
Someone learned about std::string_view, and started replacing instances of std::string const& with string_views in their C++ code base. As a result of that, a subtle bug shows up!
The Case of string_view and the Magic String
by Giovanni Dicanio
From the article:
(...) The code is recompiled and executed. But, unfortunately, now the output has changed! What’s going on here? Where does that “magic string” come from?
By Blog Staff | May 11, 2023 09:42 AM | Tags: None
Every year we run Pure Virtual C++: a free one-day virtual conference for the whole C++ community. Next month we’re doing it again! Sign-up for free to get access to our five live sessions and a host of pre-conference content.
Sign Up for the free Pure Virtual C++ 2023 Conference
by Sy Brand
From the article:
The live event will run June 6th 13:00-16:00 UTC. Videos will be available to stream for free on YouTube after the conference.
The live sessions will be:
- C++ Compiler Errors for Humans with Sy Brand
- Address Sanitizer continue_on_error with Jim Radigan
- Value-Oriented Programming with Tony Van Eerd
- Productive Cross-Platform and Game Development in Visual Studio with Sinem Akinci and David Li
- Build Time Reflection with C++ in Year 2023 with Gabriel Dos Reis
By Blog Staff | May 10, 2023 04:40 PM | Tags: None
In an earlier blog post, I showed that the Go programming language allows you to write generic functions once you have defined an interface.
Defining Interfaces in C++ with ‘Concepts’ (C++20)
by Daniel Lemire
From the article:
Java has a very similar concept under the same name (interface). I gave the following example:
type IntIterable interface { HasNext() bool Next() uint32 Reset() } func Count(i IntIterable) (count int) { count = 0 i.Reset() for i.HasNext() { i.Next() count++ } return }