The Pimpl Pattern - what you should know—Bartlomiej Filipek

A good sum up.

The Pimpl Pattern - what you should know

by Bartlomiej Filipek

From the article:

Have you ever used the pimpl idiom in your code? No matter what’s your answer read on smile

In this article I’d like to gather all the essential information regarding this dependency breaking technique. We’ll discuss the implementation (const issue, back pointer, fast impl), pros and cons, alternatives and also show examples where is it used. You’ll also see how modern C++ can change this pattern. Moreover, I hope you’ll help me and provide your examples...

Introduction to std::chrono—Rachel Crawford

How to measure time in C++?

Introduction to std::chrono

by Rachel Crawford

From the article:

How many times have you tried to call a function that alleges to return a time value only to realise you don’t know what units the value is in? Or that takes a time value as a parameter, but doesn’t specify whether the value is expected to be in milliseconds, seconds, or hours?

Quick Q: Function not called in code gets called at runtime

Quick A: undefined behaviour can result in anything.

Recently on SO:

Function not called in code gets called at runtime

The program contains undefined behavior, as dereferencing a null pointer (i.e. calling foo() in main without assigning a valid address to it beforehand) is UB, therefore no requirements are imposed by the standard.

Executing never_called at runtime is a perfect valid situation when undefined behavior has been hit, it's as valid as just crashing (like when compiled with GCC). Okay, but why is Clang doing that? If you compile it with optimizations off, the program will no longer output "formatting hard disk drive", and will just crash...

C++ Weekly Episode 96: Transparent Lambda Comparators—Jason Turner

Episode 96 of C++ Weekly.

Transparent Lambda Comparators

by Jason Turner

About the show:

In this episode Jason explores the use of lambdas as comparators for the associative containers. Just how far can we take the use of lambdas? Variadic templates, forwarding references, multiple inheritance, variadic "using" declarations, local classes, transparent comparators and direct base class initialization are all utilized in this video.

A friendly type predicate—Andrzej KrzemieĹ„ski

To improve the error messages.

A friendly type predicate

by Andrzej Krzemieński

From the article:

This is a sequel to the previous post on writing a custom type predicate. One of the readers on Reddit made a very insightful observation. The user has implemented a type that she intends to use with our library, call it Calc. She passes it to the library function, and she gets the compiler error:

static assertion failed: X does not have a desired interface

But what is our type missing? In the previous post we were describing 3 constraints. A concept could have far more of them. The user has already made an effort to have Calc comply with the constraints, so there must be something tiny missing. Maybe there is a bug in the implementation of the predicate? But it is difficult to track what it is that the predicate does not like about our type. We could use some more specific information...