c++visual-studioc++20backwards-compatibilityc++-modules

Does header file import modules a standard thing?

C++ 20 modules guaranteed backward compatible so modules can import headers.

And Visual Studio introduced header file import modules,is this stardard or just a VS thing?

// MyProgram.h
import std.core;
#ifdef DEBUG_LOGGING
import std.filesystem;
#endif
Solution

  • #include is a preprocessor directive that does a textual copy-and-paste of the text in the target file. Modules didn't change this. Textually copy-and-pasting import directives is still textual copy-and-pasting.

    So yes, this is standard. Assuming your compiler implements them correctly.

    That being said, it's probably not a good idea to have headers import things. If you want to build a collection of imports used by various files in your system, just build a proper named module and reap the benefits of the module build system. It's OK to export import modules.