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App-level Developer on std::error Exceptions Proposal for C++. Part II. The Discussion.--"No Bugs" H

By Adrien Hamelin | Jun 4, 2018 01:19 PM | Tags: experimental

Nothing is easy.

App-level Developer on std::error Exceptions Proposal for C++. Part II. The Discussion.

by "No Bugs" Hare

From the article:

For quite a long while, in certain parts of C++ community, there is a substantial resistance to existing C++ exceptions; this leads to an alternative subculture of using error codes instead of exceptions, so there are effectively two barely-compatible C++ worlds: world-using-exceptions, and world-using-error-codes...

Revisting Regular Types -- Titus Winters

By shreck | Jun 3, 2018 01:07 AM | Tags: None

An updated discussion on C++ type design, especially the overlap between Regular and reference types.

Revisiting Regular Types

By Titus Winters

From the article:

With 20 years of experience, we know that Regular type design is a good pattern - we should model user-defined types based on the syntax and semantics of built-in types where possible. However, common formulations of Regular type semantics only apply to values, and for performance reasons we commonly pass by reference in C++. In order to use such a reference as if it were its underlying Regular type we need some structural knowledge of the program to guarantee that the type isn’t being concurrently accessed. Using similar structural knowledge, we can treat some non-Regular types as if they were Regular, including reference types which don’t own their data. Under such an analysis, string_view indeed behaves as if it were Regular when applied to common usage (as a parameter). However, span does not, and further it is (currently) impossible to have shallow copy, deep compare, and Regular const semantics in the same type in C++.

This analysis provides us some basis to evaluate non-owning reference parameters types (like string_view and span) in a practical fashion, without discarding Regular design.

Automatic Object Linkage, with Include Graphs -- Thomas Young

By Thomas Young | Jun 3, 2018 01:05 AM | Tags: None

For C++ code-bases with multiple targets and shared code elements, static libraries are kind of the default approach, but is there a better way to set this up?

Automatic Object Linkage, with Include Graphs

by Thomas Young

From the article:

In this post I describe an alternative approach to sharing source code elements between multiple build targets.

 

...

We'll need to enforce some constraints on the way the source code is set up, notably with regards to header file organisation, but can then automatically determine what to include in the link operation for each build target, based on a graph of include relationships extracted from the source files.

The resulting dynamic, fine grained, object-file centric approach to code sharing avoids the need for problematic static library decomposition, and the associated 'false dependencies'.

Transforming std::find into std::ranges::find -- Christopher Di Bella

By Christopher Di Bella | Jun 3, 2018 01:04 AM | Tags: c++17

Today, we dive into what std::find does, and how we can leverage various concepts to cleanly express its requirements, as achieved in std::ranges::find.

Transforming std::find into std::ranges::find

By Christopher Di Bella

From the article:

... The code is nearly the same, but not quite. Where it differs is in how we determine the end of the sequence, how we take the successor of our current element, and how we retrieve the value. While this is conceptually the same, it’s implementationally different.

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Iterators are a topic rich with mathematics. Because they are part of what makes generic programming so powerful, this topic spans multiple chapters in books on generic programming.

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we’ll now refine find to consider the EqualityComparableWith concept that we laboured over in the last article....

Hello CMake!--Arne Mertz

By Adrien Hamelin | May 28, 2018 01:14 PM | Tags: intermediate community

Do you use it?

Hello CMake!

by Arne Mertz

From the article:

Since I have mentioned CMake in a handful of past blog posts, it is time to give a short introduction for those that don’t know it yet.

CMake is one of the most popular build systems for C++ out there. One of the main reasons probably is that it is cross-platform: It does not build the project itself but operates a platform-specific system. That means it can generate Makefiles, ninja-build files, or project files for Visual Studio or Xcode, to name just a few...

Quick Q: use of constexpr in header file

By Adrien Hamelin | May 28, 2018 01:08 PM | Tags: advanced

Quick A: const in a header implicitely means static.

Recently on SO:

use of constexpr in header file

constexpr implies const and const on global/namespace scope implies static (internal linkage), which means that every translation unit including this header gets its own copy of PI. The memory for that static is only going to be allocated if an address or reference to it is taken, and the address is going to be different in each translation unit.

That implied static for const variables was introduced specifically to use const instead of #define in header files in C++ to define constants. Without static there would be multiple symbol definitions linker error if that header file is included in more than one translation unit which were linked together.

In C++17 you can also make it inline, so that there is only ever a single copy of PI if an address or reference to it is taken (i.e. not static). inline variables were introduced in C++17 to allow for header-only libraries with non-const variable definitions in the header files.

In other words, you should use constexpr for your constants in header files, if possible, otherwise const. And if you require the address of that constant to be the same everywhere mark it as inline.

Error Handling and std::optional--Bartlomiej Filipek

By Adrien Hamelin | May 24, 2018 12:56 PM | Tags: intermediate c++17

Do you have a prefered way?

Error Handling and std::optional

by Bartlomiej Filipek

From the article:

In my last two posts in the C++17 STL series, I covered how to use std::optional. This wrapper type (also called “vocabulary type”) is handy when you’d like to express that something is ‘nullable’ and might be ‘empty’. For example, you can return std::nullopt to indicate that the code generated an error… but it this the best choice?

Declarative Functional APIs – A.K.A. Abusing Lambda Parameters--Philippe Groarke

By Adrien Hamelin | May 23, 2018 01:00 PM | Tags: c++17 advanced

Take some time to clear your thoughts before reading!

Declarative Functional APIs – A.K.A. Abusing Lambda Parameters

by Philippe Groarke

From the article:

Functional APIs are a joy to work with. Not only do they help eliminate certain bug categories, but they tend to be very flexible and reusable. Today I present a technique that has emerged while I was simplifying some lambda based APIs. C++17 makes template meta-programming much more palatable, I dare not imagine what this would look like in C++11...