The scanner will look at files in directories specified with the sonar.sources property. These files are then analyzed according to several criteria, such as the programming language but not limited to this. There are different levels of analysis, such as code coverage. For the main C/C++/Objective-C analysis, the scanner will use data from the build wrapper. A file is not fully ignored when the build wrapper has no data for it, but no C++ analysis will be done.
You can learn how to exclude some files and more here if needed:
- SonarQube: Narrowing the Focus | SonarQube Docs
- SonarCloud: Analysis Scope | SonarCloud Docs
I hope this helps.