There are often errors displayed after the indexer completes building its data base following the creation of a new project or the opening of a project not already in the workspace and again just before building. Some of these errors can be due to settings in the Eclipse Indexer settings.
In one scenario, a project which builds clean, that is, no compiler or IDE errors, will mark code lines in a source file which includes a large header file as 'cannot resolve symbol xxxx'.
In this case, the header file is larger than 17 MB. In the Eclipse Indexer settings, there are settings 'Skip files larger than' and 'Skip included files larger than'. These settings, by default, are set to 8 MB. This would be too low for the header file in this example. In order to resolve the issue, the setting should be increased to allow for the large header file to be indexed.