Quick Q: How does virtual inheritance solve the “diamond” (multiple inheritance) ambiguity?

By Adrien Hamelin | Sep 18, 2019 12:42 PM | Tags: advanced

Quick A: by making sure only one instance of each parent class is created.

Recently on SO:

How does virtual inheritance solve the “diamond” (multiple inheritance) ambiguity?

You want: (Achievable with virtual inheritance)

  A 
/ \ 
B   C 
\ / 
  D

And not: (What happens without virtual inheritance)

A   A 
|   |
B   C 
\ / 
  D

Virtual inheritance means that there will be only 1 instance of the base A class not 2.

Your type D would have 2 vtable pointers (you can see them in the first diagram), one for B and one for C who virtually inherit A. D's object size is increased because it stores 2 pointers now; however there is only one A now.

So B::A and C::A are the same and so there can be no ambiguous calls from D. If you don't use virtual inheritance you have the second diagram above. And any call to a member of A then becomes ambiguous and you need to specify which path you want to take.

New new() - The C++17's Alignment Parameter for the operator new() -- Bartlomiej Filipek

By bfilipek | Sep 18, 2019 12:42 AM | Tags: None

C++17's new and handy new operator that supports overaligned objects!

New new() - The C++17's Alignment Parameter for Operator new()

by Bartlomiej Filipek

From the article:

The whole deal about the new functionality is that you can forgot about the limitation of over-aligned data. It lets you write regular modern C++ code without worrying about specialized allocators or raw memory handling functions like std::aligned_alloc() or _aligned_malloc().

C++ Core Guidelines: Type Safety--Rainer Grimm

By Adrien Hamelin | Sep 16, 2019 12:07 PM | Tags: community

One more.

C++ Core Guidelines: Type Safety

by Rainer Grimm

From the article:

The C++ core guidelines support three profiles: type safety, bounds safety, and lifetime safety. Thanks to the guideline support library (GSL), you can check your code against these profiles. Today, I start with the profile type safety...

Back to Basics at CppCon 2019

By Adrien Hamelin | Sep 16, 2019 12:05 PM | Tags: community

It started!

Back to Basics at CppCon 2019

by Arthur O’Dwyer

From the article:

Tomorrow I’ll be flying out to Denver, Colorado, for CppCon 2019. This will be my busiest CppCon yet! Besides giving my “STL From Scratch” weekend course for the third year in a row, this year I’m also the chair of CppCon’s new “Back to Basics” track...

Quick Q: Undefined reference to static constexpr char[]

By Adrien Hamelin | Sep 16, 2019 12:01 PM | Tags: intermediate c++17 c++14

Quick A: this is no longer an issue with C++17.

Recently on SO:

Undefined reference to static constexpr char[]

Add to your cpp file:

constexpr char foo::baz[];

Reason: You have to provide the definition of the static member as well as the declaration. The declaration and the initializer go inside the class definition, but the member definition has to be separate.

C++ Core Guidelines: Profiles--Rainer Grimm

By Adrien Hamelin | Sep 11, 2019 11:43 AM | Tags: community

To continue in the next one.

C++ Core Guidelines: Profiles

by Rainer Grimm

From the article:

Informally, profiles are a subset of rules of the C++ core guidelines for specific concerns such as type safety, bounds safety, and lifetime safety. Thanks to the guideline support library, they can be checked...

Cppcon-Tool Time 2019--Jon Kalb

By Adrien Hamelin | Sep 11, 2019 11:41 AM | Tags: community

Will you attend?

Tool Time 2019

by Jon Kalb

From the article:

Similar to tech labs at some other events, we’re offering the opportunity for anyone, from an author/creator, to a vendor, to a super-user, to represent a tool (app, library, framework, or service) and run their own table answering questions or showing demos...

C++17 - The Complete Guide now complete and available -- Nicolai M. Josuttis

By Nico Josuttis | Sep 10, 2019 11:43 PM | Tags: c++17

A new the latest book by Nicolai M. Josuttis is now complete and available.

C++17 - The Complete Guide

by Nicolai M. Josuttis

About the book:

The book is a full description of all language and library features that were introduced and modified with C++17.

It contains plenty of examples and many hints from using these new features in practice.

It is availble at your local book store or here.

Replacing and overloading new and delete in MSVC v142 -- Guy Davidson

By Guy | Sep 8, 2019 11:46 PM | Tags: None

Do you know the difference between replacing and overloading?

“Searching for another overload”: overloading and replacing new and delete with MSVC v142

by Guy Davidson

From the article

There are rather a lot of operator new functions; the standard defines 22, 14 of which are non-member functions. How does the new operator know which operator new to call?

Quick Q: Removing item from vector, while in C++11 range 'for' loop?

By Adrien Hamelin | Sep 6, 2019 11:00 AM | Tags: c++11 basics

Quick A: it is not possible

Recently on SO:

Removing item from vector, while in C++11 range 'for' loop?

No, you can't. Range-based for is for when you need to access each element of a container once.

You should use the normal for loop or one of its cousins if you need to modify the container as you go along, access an element more than once, or otherwise iterate in a non-linear fashion through the container.

For example:

auto i = std::begin(inv);

while (i != std::end(inv)) {
    // Do some stuff
    if (blah)
        i = inv.erase(i);
    else
        ++i;
}