ConclusionĪs you can see, the feature is very promising, but CMake does not yet support this directly. Within the modules you can include files so legacy support is still possible as to be expected. Target_link_options(main PUBLIC "LINKER:helloworld.pcm")Įlseif (CMAKE_CXX_COMPILER_ID STREQUAL "MSVC")Īdd_compile_options(/experimental:module /c)Īs you can see the main file does not use any #include, but instead one import. Set(PREBUILT_MODULE_PATH $)Īdd_executable(mainExe main.cpp helloworld.cpp)Įlseif (CMAKE_CXX_COMPILER_ID STREQUAL "GNU") We used the ninja generator to get this built, but as a generated Makefile it should work as well: cmake_minimum_required(VERSION 3.16) We call it helloworld.cpp: module Īnd for the main.cpp we just have: import helloworld // import declarationįinally, we create a CMakeLists.txt which should work with Clang, GCC and MSVC. Now let’s check a module we created for our application. On Visual Studio side use version 19.25 or later. With Ubuntu you should wait for 22.04 LTS when it’s release or the Alpha/Beta daily build, being provided currently. With an up-to-date Arch or Manjaro that is the case. You also should ensure you have the latest version of these compilers. I am testing here GCC 11.1.0 and clang 13.0.0. GCC has been becoming better, but you need to compile system libraries into modules for your program. If you want to test it and keep opensource you should try Clang. The standard is a bit over a year old (published on Dec 2020) and unfortunately the software is WIP. Set let’s start using C++20 today! Well, not quite. No more include guards or similar compile hacks required since modules are imported only once.You can select the units you are interested, meaning what is not required will not be considered thus reducing the compile time even further. No more duplication of code passed to the compiler as import behaves differently compared to using #include with header files.It is pretty much wasted time because many of the same includes in different sources (especially in bigger projects) are passed over and over again.įinally the C++20 standard addresses that issue with modules and defines some rules similar to what is established in Fortran: The process itself is fine as we know, but with many includes and multiple files the build time gets very large, especially when standard libraries are used. Every #include means to include the whole file and pass it as whole to the sources which are to be resolved by the compiler. Well, in C and C++ we have a big problem with included header files. Real modules is a different thing, read on!įor at least since 1990 modules have been used in the Fortran language, so the idea is pretty old, but why care? obj files are modules, and it gets confused when talking about modularisation. Starting with the word „Modules“, I have heard that.
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