The IntelliSense configuration provider uses the "closest path" lookup method to find which compile command is closest to the open file. Unfortunately, the build system would occasionally use a capital letter for the drive (C:\), which the C++ extension never does. This caused all lookups to fail, as they had no parts in common with the commands' files. As a result, C and C++ files were parsed with the compilation flags for one of the kernel files, which did not match the flags the application files were compiled with.