Tells the compiler to use an existing IFC (.ifc) for the current compilation.

/module:reference module-name=filename
/module:reference filename

filename
The name of a file that contains IFC data, prebuilt module information. To import more than one module, include a separate /module:reference option for each file.

module-name
A valid name of an exported primary module interface unit name or full module partition name.

The /module:reference compiler option requires you enable experimental modules support by use of the /experimental:module compiler option, along with the /std:c++latest option. This option is available starting in Visual Studio 2019 version 16.8.

If the /module:reference argument is a filename without a module-name, the file gets opened at runtime to verify the filename argument names a specific import. It can result in slower runtime performance in scenarios that have many /module:reference arguments.

The module-name must be a valid primary module interface unit name or full module partition name. Examples of primary module interface names include:

• M
• M.N.O
• MyModule
• my_module

Examples of full module partition names include:

• M:P
• M.N.O:P.Q
• MyModule:Algorithms
• my_module:algorithms

If a module reference is created using a module-name, other modules on the command line don't get searched if the compiler encounters an import of that name. For example, given this command line:

cl ... /experimental:module /module:reference m.ifc /module:reference m=n.ifc

In the case above, if the compiler sees import m; then m.ifc doesn't get searched.

Given three modules as listed in this table:

The reference options using a filename argument could look like:

cl ... /experimental:module /module:reference m.ifc /module:reference m-part.ifc /module:reference Networking.ifc

The reference options using module-name=filename could look like:

cl ... /experimental:module /module:reference m=m.ifc /module:reference M:Part1=m-part.ifc /module:reference Core.Networking=Networking.ifc

1. Open the project's Property Pages dialog box. For details, see Set C++ compiler and build properties in Visual Studio.

2. Set the Configuration drop-down to All Configurations.

3. Select the Configuration Properties > C/C++ > Command Line property page.

4. Modify the Additional Options property to add the /module:reference option and its arguments. Then, choose OK or Apply to save your changes.

/experimental:module (Enable module support)
/headerUnit (Use header unit IFC)
/module:exportHeader (Create header units)
/translateInclude (Translate include directives into import directives)