C++20 Modules in Shared Libraries

Question

Hello,

Follow-up question to https://learn.microsoft.com/en-us/answers/questions/1665106/how-to-use-c-20-modules-in-shared-libraries

I’ve been exploring the use of C++20 modules in shared libraries and I understand the typical approach involves providing an .ifc file. However, I’m curious if there’s a way to utilize these modules without distributing the .ifc file. Could you provide guidance on how to use a DLL module in such a scenario?

• Alternative Methods: Are there alternative methods to import modules without an .ifc file?
• DLL Usage: How can one use the DLL module without the .ifc file in another project?
• Build System Configuration: What changes are needed in the build system to support this usage?

Any insights or examples would be greatly appreciated

Thank you!

Answer 1

Hi,

After testing

Alternative Methods:

1. Providing forward declarations

Since the source file has been compiled into a DLL, all you need to do is provide the necessary declarations.

main.cpp

 void myFunction();
 class  Test;
   class Test
 {
 public:
     Test();
 };
//import test.modules;
int main()
{
    myFunction();
    Test();
}

Or 2. Right click project -> Add -> Existing item: your test.modules.ixx file to the project. (test.modules.cpp file is not needed)

import test.modules;
int main()
{
    myFunction();
    Test();
}

The compiler will generate an ifc file for use in your project.

Also, don't forget to link to the DLL.

Best regards,

Minxin Yu

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