I don't get why my Intellisense keeps giving me error and other hints

[Simone Vollaro (slim71)]

Hi all,
I don't know whether this is a bug or rather something I'm doing/understanding wrong, so here goes.

I have a ROS2 project I'm developing mainly in C++, using VSCode and the C/C++ extension. Here's a link to the complete project, if needed, but I'll post the important details here.

I have the following c_cpp_properties.json file

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/src/pelican/**",
                "${workspaceFolder}/src/datapad/**",
                "${workspaceFolder}/src/Micro-XRCE-DDS-Agent/include/uxr/agent/**",
                "/opt/ros/humble/include/**",
                "${workspaceFolder}/install/comms/include/**",
                "${workspaceFolder}/install/px4_msgs/include/px4_msgs/**",
                "${workspaceFolder}/install/px4_ros_com/include/px4_ros_com/**",
                "/home/slim71/Documents/git/pugixml",
                "/usr/include/**",
                "/usr/include/",
                "/usr/local/include/**",
                "/usr/local/include/"
            ],
            "defines": [],
            "cStandard": "c11",
            "cppStandard": "c++17",
            "intelliSenseMode": "${default}",
            "compileCommands": "${workspaceFolder}/build/compile_commands.json"
        }
    ],
    "version": 4,
    "enableConfigurationSquiggles": true
}

and this settings.json file

{
  "C_Cpp.clang_format_path": "/usr/bin/clang-format-17",
  "C_Cpp.clang_format_style": "file:${workspaceFolder}/.vscode/.clang-format",
  "C_Cpp.default.cStandard": "c17",
  "C_Cpp.default.cppStandard": "c++17",
  "C_Cpp.default.intelliSenseMode": "linux-gcc-x64",
  "C_Cpp.formatting": "clangFormat",
  "C_Cpp.intelliSenseEngine": "default",
  "[python]": {
    "editor.defaultFormatter": "ms-python.black-formatter",
    "editor.detectIndentation": false,
    "editor.insertSpaces": true,
    "editor.tabSize": 4
  },
  "autopep8.args": [
    "\"--max-line-length=100\""
  ],
  "clang-format.executable": "/usr/bin/clang-format-17",
  "editor.foldingStrategy": "indentation",
  "python.analysis.extraPaths": [
    "/opt/ros/humble/lib/python3.10/site-packages",
    "/opt/ros/humble/local/lib/python3.10/dist-packages"
  ],
  "python.analysis.typeCheckingMode": "basic",
  "python.autoComplete.extraPaths": [
    "/opt/ros/humble/lib/python3.10/site-packages",
    "/opt/ros/humble/local/lib/python3.10/dist-packages"
  ],
  "python.envFile": "${workspaceFolder}/.env",
  "ros.distro": "humble",
  "ros.isolateEnvironment": false,
  "ros.rosSetupScript": "${workspaceFolder}/install/setup.bash",
  "search.exclude": {
    "**/*.code-search": true,
    "**/bower_components": true,
    "**/build": true,
    "**/install": true,
    "**/log": true,
    "**/node_modules": true
  },
  "uncrustify.configPath.linux": "/opt/ros/humble/lib/python3.10/site-packages/ament_uncrustify/configuration/ament_code_style.cfg",
  "editor.foldingImportsByDefault": true,
  "clang-format.fallbackStyle": "",
  "C_Cpp.default.compilerPath": "/usr/bin/gcc",
  "files.associations": 
    # deleted to make this shorter
  },
  "todo-tree.general.debug": true,
  "todo-tree.tree.scanMode": "workspace only",
  "todo-tree.general.tags": [
    # deleted to make this shorter
  ]
}

As you can see, I'm using a compile_commands.json file (generated by colcon) though I'm still new to this, and I've also set the includePath value with all folders in which I have possible used includes.
Right now most of the code seems to be recognized, but I still have some red squiggles saying "cannot open source file math.h"


and the functions definitions seem not to be found.
I've tried adding the compilerPath setting, linking to /usr/bin/gcc, but strangely enough that seems to make things worse: the scan job seems to be spinning forever and it won't complete. I guess there's too much to scan?

EDIT: after a long time, it finished scanning but things are not looking good: now the issue for math.h is fine, it seems, but it says functions definitions are not found. I have found this issue which might be related to this though, so I think using compilerPath is a no-go for now...

So now I'm trying to understand how I can get rid of the error for math.h (which of course is present in /usr/include/) to get everything nice and clear.
Any suggestions? 😄

EDIT2: some details:
VSCode version: 1.85.2
C/C++ extension version: 1.18.5