Intellisense expects an indentifier when using C pre... | microsoft/vscode-cpptools

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Bug type: Language Service

In a project I am working on (Varnish Cache), there is commonly used preprocessor pattern where indentifier values are put into a seperate header value and included into the actual definition (this lets you get the indentifier later as a string value in code and other things). Intellisense seems to not like this pattern, reporting errors in both the C file and the H file:

expected an identifier C/C++ (40)

Here is a reproducible test case:

// test.c

enum test
{
#define TM(name) t_ ## name,
#include "test.h"
};

int main()
{
	enum test t = t_two;

	return (t == t_one);
}

// test.h

TM(one)
TM(two)
#undef TM

The Intellisense errors are reported at the end of the enum definition in the C file and at the end of the H file. This compiles fine on most every C compiler I have used.

VS Code version: Code 1.63.1 (fe719cd3e5825bf14e14182fddeb88ee8daf044f, 2021-12-14T02:02:02.183Z)
OS version: Linux x64 5.11.0-41-generic snap
Restricted Mode: No

C/C++: Log Diagnostics

-------- Diagnostics - 12/14/2021, 2:11:49 PM
Version: 1.8.0-insiders2
Current Configuration:
{
    "name": "Linux",
    "includePath": [
        "${workspaceFolder}/**"
    ],
    "defines": [],
    "compilerPath": "/usr/bin/gcc",
    "cStandard": "gnu17",
    "cppStandard": "gnu++14",
    "intelliSenseMode": "linux-gcc-x64",
    "compilerArgs": [],
    "intelliSenseModeIsExplicit": false,
    "cStandardIsExplicit": false,
    "cppStandardIsExplicit": false,
    "mergeConfigurations": false,
    "compilerPathIsExplicit": false,
    "browse": {
        "path": [
            "${workspaceFolder}/**"
        ],
        "limitSymbolsToIncludedHeaders": true
    }
}
Translation Unit Mappings:
[ /home/reza/Code/test/vstest/test.c ]:
    /home/reza/Code/test/vstest/test.h *
    /home/reza/Code/test/vstest/test.c
Translation Unit Configurations:
[ /home/reza/Code/test/vstest/test.c ]:
    Process ID: 108590
    Memory Usage: 12 MB
    Compiler Path: /usr/bin/gcc
    Includes:
        /usr/lib/gcc/x86_64-linux-gnu/9/include
        /usr/local/include
        /usr/include/x86_64-linux-gnu
        /usr/include
    Standard Version: c17
    IntelliSense Mode: linux-gcc-x64
    Other Flags:
        --gcc
        --gnu_version=90300
Total Memory Usage: 12 MB

------- Workspace parsing diagnostics -------
Number of files discovered (not excluded): 2509

System Info

Item	Value
CPUs	11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz (8 x 1800)
GPU Status	2d_canvas: unavailable_software gpu_compositing: disabled_software multiple_raster_threads: enabled_on oop_rasterization: disabled_off opengl: disabled_off rasterization: disabled_software skia_renderer: enabled_on video_decode: disabled_software vulkan: disabled_off webgl: unavailable_software webgl2: unavailable_software
Load (avg)	1, 1, 1
Memory (System)	15.37GB (8.31GB free)
Process Argv	--no-sandbox --force-user-env --unity-launch --crash-reporter-id f6d4888a-1739-431b-aa18-f552c065d1ff
Screen Reader	no
VM	0%
DESKTOP_SESSION	ubuntu
XDG_CURRENT_DESKTOP	Unity
XDG_SESSION_DESKTOP	ubuntu
XDG_SESSION_TYPE	x11

Extensions (3)

Extension	Author (truncated)	Version
remote-ssh	ms-	0.70.0
cpptools	ms-	1.8.0-insiders2
cpptools-extension-pack	ms-	1.1.0

(1 theme extensions excluded)

Reproduce the diagnostic with the issue's test.c and test.h files using the C/C++ IntelliSense configuration described in the report. Start by tracing how the language service processes the enum, macro, and included header; done means the valid preprocessor pattern no longer produces the reported errors in either file.

Written by the indexing model from the issue text.

Intellisense expects an indentifier when using C preprocessor

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