How do you fix Intellisense errors in a CMake project when Visual Studio is connected to WSL:Ubuntu?

Brandon Davies-Sekle 0

I am running a CMake project in Visual Studio Community 2026 and it is connected to WSL: Ubuntu. It is running the Linux Debug configuration preset. WSL is running the gcc 15.1.0 compiler.

My C++ code builds and runs fine but I get hundreds of false-positive Intellisense errors. One example is the following:

Severity Code Description Project File Line Suppression State Details

Error (active) E0020 identifier "_Float32" is undefined CppProgUbuntu - Linux Debug C:\Users\bsekl\AppData\Local\Microsoft\Linux\HeaderCache\1.0\Ubuntu\opt\gcc-15\include\c++\15.1.0\atomic 1692

It is apparent that this is happening because Intellisense is not using the correct system headers and preprocessor definitions for the target environment.

How do I fix this so that Intellisense functions properly and doesn't report false-positive errors?

7 answers

Varsha Dundigalla(INFOSYS LIMITED) 3,960 Reputation points Microsoft External Staff

2025-12-12T11:05:13.02+00:00
Thank you for reaching out.

Visual Studio IntelliSense is still using the wrong compiler settings. Even though you added all the include paths and flags, IntelliSense decides which compiler to mimic based on the PATH environment in your CMake preset. If /opt/gcc-15/bin is not first in PATH, IntelliSense falls back to /usr/bin/g++ and ignores the GCC 15 macros (like _Float32), so the squiggles remain.

Add PATH override in your preset In your linux-debug preset, add: "environment": { "PATH": "/opt/gcc-15/bin:${penv:PATH}" } Show more lines This makes sure Visual Studio queries GCC 15 for IntelliSense instead of the default compiler.

Keep these settings you already did:

intelliSenseMode: "linux-gcc-x64"

CMAKE_EXPORT_COMPILE_COMMANDS: ON

copyAdditionalIncludeDirectoriesList and additionalCompilerArgs with -isystem paths.

Clean and rebuild caches:

Close the folder in Visual Studio.

Delete %LOCALAPPDATA%\Microsoft\Linux\HeaderCache\1.0\Ubuntu.

Reopen the project → Delete Cache and Reconfigure → Build All.

Verify detection: After reconfigure, check the CMake output in Visual Studio. It should show:
C++ compiler: /opt/gcc-15/bin/g++
If it still shows /usr/bin/g++, the PATH override didn’t apply.

The missing piece is making /opt/gcc-15/bin the first entry in PATH for your preset. Without that, IntelliSense keeps using the wrong compiler macros, causing false errors.

Please let us know if you require any further assistance, we’re happy to help.

If you found this information useful, kindly mark this as "Accept Answer".
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Varsha Dundigalla(INFOSYS LIMITED) 3,960 Reputation points Microsoft External Staff

2025-12-12T15:37:10.7566667+00:00

If you need more support on coding-related topics, kindly create a thread with the Git team so they can assist you further. Create a Case | Phone Support | Service Hub

Please note that we don’t write/cannot provide our own scripts, especially without disclaimers, error handling, proper testing, etc. We can supply the necessary command lines/information, but it is recommended to work with your internal team to create and implement scripts based on those commands/information. As your internal team will be best to understand your project and environment requirements.

Brandon Davies-Sekle 0 Reputation points

2025-12-12T16:34:30.7566667+00:00

Hi Varsha. Thanks for your reply. After adding "environment": {`` ``"PATH": "/opt/gcc-15/bin:${penv:PATH}"`` ``} to the linux-debug preset, I got the error CmakeSettings Error at CMakePresets.json Failed to evaluate macro '${penv:PATH}' after Cmake tried to reconfigure. Do you know how I might resolve this? Is there a syntax error? Thanks again.

Varsha Dundigalla(INFOSYS LIMITED) 3,960 Reputation points Microsoft External Staff

2025-12-12T16:52:19.87+00:00

Thank you for reaching out.

The earlier steps were correct for include paths and compiler arguments, but IntelliSense still used the wrong compiler because the PATH override wasn’t applied. The macro syntax was invalid, so Visual Studio kept falling back to /usr/bin/g++ instead of /opt/gcc-15/bin/g++. That’s why the errors like _Float32 remained.

Here’s the right way to fix it:

In your CMakePresets.json, update the environment block to: "environment"``: { ``"PATH": "/opt/gcc-15/bin:$penv{PATH}" } use $penv{PATH} (no colon) and separate entries with : for Linux. This ensures /opt/gcc-15/bin comes first, so IntelliSense queries GCC 15.

After saving:

Close Visual Studio.

Delete %LOCALAPPDATA%\Microsoft\Linux\HeaderCache\1.0\Ubuntu.

Reopen the project, select the Linux Debug preset.

Run Delete Cache, then Reconfigure, then Build All.

Check the CMake output—compiler should show /opt/gcc-15/bin/g++.

Once PATH is correct, IntelliSense uses the same compiler and headers as your WSL build, and those false errors will disappear.

Please let us know if you require any further assistance, we’re happy to help.

If you found this information useful, kindly mark this as "Accept Answer".

Brandon Davies-Sekle 0 Reputation points

2025-12-15T16:11:21.4333333+00:00

Hi Varsha. Thanks for your reply. After adding "environment": { "PATH": "/opt/gcc-15/bin:$penv{PATH}" to my CMakePresets.json, Cmake was able to properly configure. However, after following steps 1-4 in your comment, Visual Studio is still showing the false-positive Intellisense errors. My CMake output is attached here: CMake Output.txt

The output doesn't appear to explicitly show that /opt/gcc-15/bin/g++ was used for the compiler. My modified CMakePresets.json is attached here: CMakePresets.txt

Do you know what steps I might take next to resolve the issue?
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Gade Harika (INFOSYS LIMITED) 2,175 Reputation points Microsoft External Staff

2025-12-16T11:14:00.7933333+00:00

Thanks for reaching out.
I’ve updated your CMakePresets.json to explicitly set compilerPath: /opt/gcc-15/bin/g++ and queryCompilerForIncludes: true. This ensures IntelliSense queries GCC 15 for builtin and system includes, matching your build configuration. After replacing the preset, please close VS, delete the Linux header cache on Windows, remove the remote .vs folder, then Delete Cache → Reconfigure → Build All. In CMake Diagnostics, confirm CMAKE_CXX_COMPILER is /opt/gcc-15/bin/g++ and PATH begins with /opt/gcc-15/bin. With the driver pinned and caches refreshed, the _Float32 and related false positives should be gone. If anything persists, share the updated CMake Diagnostics and compile_commands.json

Apply_Instructions (1).txt
CMakePresets.updated1.txt

Let us know if the issue persists after following these steps. I’ll be happy to assist further if needed. If the issue has been resolved, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.
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How do you fix Intellisense errors in a CMake project when Visual Studio is connected to WSL:Ubuntu?

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