I was not able to reproduce this issue in 11.0.1, but, I did have to make a minor change to your example, since "DoSomething" was not being recognized as a prototype since it's return type was missing.
If this is more than a typo in your example, I suggest setting "def_ctags_flags" (Macro > Set Macro Variable...) to 6, which turns on a flag that tells our parser not to ignore old style C prototypes with missing return types.
--Dennis