Issue with __VA_OPT__() keyword not expanding properly in a variadic macro

Bug type: Language Service

Describe the bug

• OS and Version: Linux Ubuntu 20.04
• VS Code Version: 1.60.2
• C/C++ Extension Version: v1.7.1
• Other extensions you installed (and if the issue persists after disabling them): Python, Pylance, PlatformIO, Shader language support for VS Code, Todo+, Jupyter (after disabling all, the problem still persists).
• If using SSH remote, specify OS of remote machine:
• A clear and concise description of what the bug is, including information about the workspace (i.e. is the workspace a single project or multiple projects, size of the project, etc).
  I was trying to program a C++ variadic macro that would print an error message to stderr like this:

#define __pError(message, ...) \
{\
    fprintf(stderr, "\x1B[31mERROR: Error at file %s, line %d:\x1B[0m ",\
            __FILE__, __LINE__);\
    fprintf(stderr, message __VA_OPT__(,) __VA_ARGS__);\
    fprintf(stderr, "\n");\
    exit(-1);\
}

I then used the macro like this:

__pError("I am going to produce an error!");

Now, this should work, but instead I get an error message:
" expected a ')' "
When I compile my project using g++, I don't get errored out; it compiles just fine.
I think the problem is with the VA_OPT() keyword; maybe it isn't implemented?

Steps to reproduce

1. Make a file, let's call it file.h
2. Paste the macro definition code into said file.
3. At the top, put #pragma once, #include <stdio.h> and #include <stdlib.h>.
4. Make another file, let's call it main.cpp.
5. Insert #include <file.h> at the top
6. Update includePath in VSCode cpp configuration files to include file.h.
7. Put in a main function:

int main()
{
    __pError("Why am I recieving an error?");

    return 0;
}

8. See error

Expected behavior

There should be no error; no red squiggly lines.

Code sample and logs

• Code sample
  file.h:

#pragma once

#define __pError(message, ...) \
{\
    fprintf(stderr, "\x1B[31mERROR: Error at file %s, line %d:\x1B[0m ",\
            __FILE__, __LINE__);\
    fprintf(stderr, message __VA_OPT__(,) __VA_ARGS__);\
    fprintf(stderr, "\n");\
    exit(-1);\
}

main.cpp:

#include "file.h"

int main()
{
    __pError("Why am I recieving an error?");

    return 0;
}

• Configurations in c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/include"
            ],
            "defines": ["GL_GLEXT_PROTOTYPES"],
            "compilerPath": "/usr/bin/gcc",
            "cStandard": "gnu17",
            "cppStandard": "gnu++14",
            "intelliSenseMode": "linux-gcc-x64"
        }
    ],
    "version": 4
}

• Logs from running C/C++: Log Diagnostics from the VS Code command palette

-------- Diagnostics - 10/30/2021, 6:54:58 PM
Version: 1.7.1
Current Configuration:
{
    "name": "Linux",
    "includePath": [
        "${workspaceFolder}/include"
    ],
    "defines": [
        "GL_GLEXT_PROTOTYPES"
    ],
    "compilerPath": "/usr/bin/gcc",
    "cStandard": "gnu17",
    "cppStandard": "gnu++14",
    "intelliSenseMode": "linux-gcc-x64",
    "compilerPathIsExplicit": true,
    "cStandardIsExplicit": true,
    "cppStandardIsExplicit": true,
    "intelliSenseModeIsExplicit": true,
    "compilerArgs": [],
    "mergeConfigurations": false,
    "browse": {
        "path": [
            "${workspaceFolder}/include",
            "${workspaceFolder}"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
Translation Unit Mappings:
[ /home/ben/c/game/src/test.cpp ]:
    /home/ben/c/game/src/test.cpp
    /home/ben/c/game/include/Utils.h
Translation Unit Configurations:
[ /home/ben/c/game/src/test.cpp ]:
    Process ID: 40704
    Memory Usage: 14 MB
    Compiler Path: /usr/bin/gcc
    Includes:
        /home/ben/c/game/include
        /usr/include/c++/9
        /usr/include/x86_64-linux-gnu/c++/9
        /usr/include/c++/9/backward
        /usr/lib/gcc/x86_64-linux-gnu/9/include
        /usr/local/include
        /usr/include/x86_64-linux-gnu
        /usr/include
    Defines:
        GL_GLEXT_PROTOTYPES
    Standard Version: c++14
    IntelliSense Mode: linux-gcc-x64
    Other Flags:
        --g++
        --gnu_version=90300
Total Memory Usage: 14 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 5969

• Logs from the language server logging

Screenshots

None should be needed, but some can be provided if necessary.

Additional context

If more context is needed, I can provide, but I don't think any more is necessary.

Inizia riproducendo la diagnostica della macro da file.h e main.cpp con il c_cpp_properties.json fornito, quindi confronta lo standard C++ configurato con il comportamento del compilatore. Traccia il modo in cui il servizio del linguaggio analizza VA_OPT in questa macro variadica. Il lavoro è completato quando l’esempio fornito viene accettato senza l’errore di parentesi di chiusura segnalato, preservando il comportamento diagnostico esistente.