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c++c++20

Can't use iostream as module in C++20 (Visual Studio)

I can't get this code running in the newest version of MSVC. This code example is from the book called "Beginning C++20, From Novice to Professional" by Ivor Horton and Peter Van Weert.

import <iostream>;

int main()
{
    int answer {42};
    std::cout << "The answer to life, universe, and everything is "
              << answer
              << std::endl;
    return 0;
}

I get this error:

could not find header unit for 'C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.28.29333\include\iostream'

I am using Microsoft Visual Studio version 16.8.1, and have enabled these flags in project properties (according to the similar question Standard way of importing modules):

  • /experimental:module
  • /std:c++latest
  • /EHsc
  • /MD

Should I use Clang or GCC instead?

Solution

  • The authors stated in the example and solution files provided for download, that due to compilers' implementations of the C++20-standard the files might not work yet (see the book's page for details and corresponding GitHub repository).

    Therefore they provide "no modules" examples which use the "#include" directive.