Gabriel Dos Reis

<h1>existing practice and Challenges</h1>

• build time scalability of idiomatic C++

Fragile and Outdated Linking Mode

Program = collection of independently translated source files

Macros are a big problem

Modules accepted for C++20

What did we accomplish

• Languate notions and constructs
• Componentization
• Isolation
• Build throughput
• Semantics-aware developer tools
• With transition paths
• Global module fragments
• Header units

Module Definition (101)

export module BasicPlane.Figures;
export struct X ...

#include <iostream>
import BasicPlane.Figures;



How does it work?

• The generated module generates .o plus metadata
• If name is not exported it is not available

Efficient Pimpl

• module :private;

Spreading Module Definition

• “export module” gives module definition
• “module X” is implementation

Spreading Module Interface

• Primary module interface


export module BasicPlane.Figures;
export import :PointPart;
export import :RectPart;

export module BasicPlane.Figures:PointPart;
export struct Point {...};

export module BasicPlane.Figures:RectPart;
import :PointPart;
export struct Rectangle {...};
export int width(const Rectangle &); ...



Module Aggregation

export module BasicPlane;

export import BasicPlane.Figures;
export import BasicPlane.Transformations;
export import BasicPlane.Canvas;

Transitioning into modular world, and preparing for modules

module;
#include <sys/stat.h>

export module System.File.Ops;
namespace Sys {
    export stat stat_dierctory(const char *);

    export using ::chmod;
}

Heder Unit: An almost module

import <iostream>
import BasicPlane.Figures;

Kicking the Tires with MSVC, GCC, and clang

gcc.gnu.org/wiki/cxx-modules

Questions

• Does

  import <iostream>

  obsolete pre-compiled headers? Yes

• PCH vs usual include. 10 times faster