\brief Called periodically to check whether indexing should be aborted. Should return 0 to continue, and non-zero to abort.
\brief Called at the end of indexing; passes the complete diagnostic set.
\brief Called when a AST file (PCH or module) gets imported.
\brief Called to index a reference of an entity.
\brief Called when a file gets \#included/\#imported.
\brief Called at the beginning of indexing a translation unit.
\brief A group of callbacks used by #clang_indexSourceFile and #clang_indexTranslationUnit.