I'm trying to dabble with the c 20 modules feature and would like to import the standard library headers as modules. Currently I have

import <iostream>;

int main()
{
    std::cout << "hello world!" << std::endl;
    return 0;
}

and I run the commands

g  -11 -fmodules-ts -std=c  20 -xc  -system-header iostream
g  -11 -fmodules-ts -std=c  20 -o program main.cpp

This gives a perfectly functioning hello world program and a module file at gcm.cache/usr/include/c /11/iostream.gcm. But vscode complains:

"iostream" is not an importable header

My c_cpp_properties.json file is

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": [],
            "compilerPath": "/usr/bin/g  -11",
            "cStandard": "c17",
            "intelliSenseMode": "linux-clang-x64",
            "cppStandard": "c  20"
        }
    ],
    "version": 4
}

Possible solutions that I don't know how to implement:

• A way to tell vscode where this iostream.gcm file is
• An alternative way of doing this where the iostream.gcm object ends up somewhere vscode already knows

CodePudding user response：

This is the known IntelliSense issue.

When importing C 20 modules or header units in C source:

• You may not see IntelliSense completions or colorization.
• You may see red squiggles that don’t match the compiler.

Status (as of June 2022)

Workaround

#if __INTELLISENSE__
#include <iostream>
#else
import <iostream>;
#endif