microsoft / microsoft/vscode-cpptools

Single `#include` inside of array causes VSCode to report the "expected an expression" error

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bug Language Service parser Visual Studio
Dominant language
TypeScript
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Description

Environment
  • OS and Version: Windows 11 24H2 (Build 26100.4349)
  • VS Code Version: 1.101.2
  • C/C++ Extension Version: 1.26.3
Bug Summary and Steps to Reproduce
Bug Summary:

I'm currently working on a project that combines an X macro with an #include statement to populate an array from a generated file, like this:

// main.c
#include <stdio.h>

#define X(n) n
int array[] = {
#include "file.txt"
    // 0
};  // "expected an expression"
#undef X

int main() {
    for (int i = 0; i < 3; i++)
    {
        printf("%i\n", array[i]);  // Output is "123", as expected.
    }
    return 0;
}

// file.txt
X(1),
X(2),
X(3),

It feels hackish, but it compiles and runs. However, VSCode doesn't seem to like the fact that array has nothing but #include "file.txt" inside. Uncommenting 0 makes the error go away, although, this obviously makes array to have 4 items instead of intended 3.

Steps to reproduce:
  1. Create main.c and file.txt and insert code above;
  2. Open main.c in VSCode;
  3. Notice error on line 7.
Expected behavior:

VSCode should understand that #include "file.txt" with expanded macros provide an expected expression.

Configuration and Logs
-------- Diagnostics - 6/30/2025, 1:54:07 AM
Version: 1.26.3
Current Configuration:
{
    "name": "Win32",
    "includePath": [
        "${workspaceFolder}/**"
    ],
    "defines": [
        "_DEBUG",
        "UNICODE",
        "_UNICODE"
    ],
    "windowsSdkVersion": "10.0.26100.0",
    "compilerPath": "cl.exe",
    "cStandard": "c17",
    "cppStandard": "c++17",
    "intelliSenseMode": "windows-msvc-x64",
    "compilerPathInCppPropertiesJson": "cl.exe",
    "intelliSenseModeIsExplicit": false,
    "cStandardIsExplicit": false,
    "cppStandardIsExplicit": false,
    "mergeConfigurations": false,
    "recursiveIncludes": {},
    "recursiveIncludesReduceIsExplicit": false,
    "recursiveIncludesPriorityIsExplicit": false,
    "recursiveIncludesOrderIsExplicit": false,
    "compilerPathIsExplicit": false,
    "browse": {
        "limitSymbolsToIncludedHeaders": true
    }
}
Modified Settings:
{
    "C_Cpp.autocompleteAddParentheses": true,
    "C_Cpp.formatting": "clangFormat",
    "C_Cpp.clang_format_fallbackStyle": "{ BasedOnStyle: Google, IndentWidth: 4, AlignAfterOpenBracket: BlockIndent, BinPackArguments: false, PenaltyBreakAssignment: 64 }",
    "C_Cpp.codeAnalysis.clangTidy.enabled": true
}
Additional Tracked Settings:
{
    "editorTabSize": 4,
    "editorInsertSpaces": true,
    "editorAutoClosingBrackets": "languageDefined",
    "filesEncoding": "utf8",
    "filesAssociations": {},
    "filesExclude": {
        "**/.git": true,
        "**/.svn": true,
        "**/.hg": true,
        "**/.DS_Store": true,
        "**/Thumbs.db": true
    },
    "filesAutoSaveAfterDelay": false,
    "editorInlayHintsEnabled": true,
    "editorParameterHintsEnabled": true,
    "searchExclude": {
        "**/node_modules": true,
        "**/bower_components": true,
        "**/*.code-search": true
    },
    "workbenchSettingsEditor": "ui"
}
cpptools version (native): 1.26.3.0
Current database path: C:\USERS\OPERATOR\APPDATA\LOCAL\TEMP\{4514E1A3-0F0D-4E39-A2F4-4D7081E65254}\.BROWSE.VC.DB
Translation Unit Mappings:
[ C:\Users\operator\Desktop\repos\test\main.c - source TU]:
    C:\Users\operator\Desktop\repos\test\file.txt
Translation Unit Configurations:
[ C:\Users\operator\Desktop\repos\test\main.c ]
    Process ID: 11608
    Memory Usage: 63 MB
    Compiler Path: C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\bin\Hostx64\x64\cl.exe
    Include paths:
        include: C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\include
        include: C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Auxiliary\VS\include
        include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt
        include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um
        include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared
        include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\winrt
        include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\cppwinrt
        include: C:\Program Files (x86)\Windows Kits\NETFXSDK\4.7.2\Include\um
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\um
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\ucrt
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\shared
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\winrt
        system include: C:\Program Files (x86)\Windows Kits\10\Include\10.0.26100.0\cppwinrt
    Defines:
        _DEBUG
        UNICODE
        _UNICODE
    Standard Version: ms_c17
    IntelliSense Mode: windows-msvc-x64
    Other Flags:
        --using_directory
        C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\lib\x86
        --using_directory
        C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.43.34808\lib\x86\store\references
        --using_directory
        C:\Program Files (x86)\Windows Kits\10\UnionMetadata\10.0.26100.0
        --using_directory
        C:\Program Files (x86)\Windows Kits\10\References\10.0.26100.0
        --using_directory
        C:\Windows\Microsoft.NET\Framework\v4.0.30319
Total Memory Usage: 63 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 5082
Number of files parsed: 238
Other Extensions

No response

Additional context

No response

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the main.c and file.txt reproducer using the reported VS Code, C/C++ extension, and cl.exe configuration, then compare compiler behavior with the IntelliSense diagnostic. Done means the include-expanded array is accepted without the "expected an expression" error while retaining the three intended elements.

Written by the indexing model from the issue text.

Assessment

Tech stack
c, typescript
Domain
devtools
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
35/100

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