clang code model has problems in C context

one of my project has a mixture of both c and c++ source files. qtc has the notion of the "active parse context" when opening a header file in qtc, to select if a header should be parsed in for a target in a c or in a c++ context.

on macos i'm seeing a funny problem:

• the file is parsed nicely when using the c++ parse context
• the file is parsed nicely when there target does not have different c and c++ contexts (all c or all c++)
• when using the c parse context of a target that has both c and c++, the IDE shows a "parse error" about macos system headers. e.g. `MacTypes.h` cannot be found