Passing information onto CMake in VSCode happens in the settings.json file.

You need to install the CMake Tools extention first.

Then, open the command pallet in VSCode with Ctrl+Shift+P and type Open Settings.

Once selected, VSCode will show a settings.json file where you should add cmake.configureArgs e.g.:

{
 "other":"settings",
 "cmake.configureArgs": [
        "-DOPTIONA=ON",
        "-DOPTIONB=ON"
    ],
}

The cmake.configureArgs array of arguments is the same as you would normally use during a command-line cmake configure e.g.

cmake -DOPTIONA=ON -DOPTIONB=ON ..

In general, command line arguments can be given by specifying cmake.configureArgs in the settings.json file, as shown by Jan Gabriel's answer.

But there is another setting (also in settings.json) specifically for -D arguments:

{
    "cmake.configureSettings": {
        "OPTIONA": "ON",
        "OPTIONB": "ON"
    }
}

See https://vector-of-bool.github.io/docs/vscode-cmake-tools/settings.html

Ideally, use a CMakePresets.json instead of mixing cmake configuration with general purpose configuration in your .vscode/settings.json

If you configure your VSCode + C++ project using cmake, you can configure all cmake configuration options in a file called CMakePresets.json.

This is preferable as it separates general purpose configuration which may be placed in .vscode/settings.json from cmake specific configuration which should be placed in its own configuration file.

This has the additional advantage that CMakePresets.json can be used with cmake via the command line directly to build the whole project in a single step.

Further information can be found by following the links below.

• https://code.visualstudio.com/docs/cpp/cmake-linux
• https://code.visualstudio.com/docs/cpp/cmake-quickstart

Disclaimer: I am not an expert in this area. I just happened to figure some relevant stuff out today using these docs.