Eclipse CDT: Upfront indexing values cause code completion clutter

I have a problem where I can't remove all of the upfront indexing values from Eclipse CDT. My C/C++ > Indexer > Files to index upfront setting is empty, however, the indexer is definitely still indexing files upfront. This means that my code completion dropdown is full of 100's of C functions which I have no desire for. What's worse is that they appear before the correct entries in code completion, meaming it's impossible to see at a glance the stuff I do want to look at.

The culprit seems to be the following code in the cdt class: parser.org.eclipse.cdt.internal.core.pdom.indexer.IndexerPreferences

private static final String DEFAULT_FILES_TO_PARSE_UP_FRONT= 
    "cstdarg, cstdio, sys/resource.h, ctime, stdarg.h, stddef.h, sys/types.h";

However, I can't find any way to change this "setting", if it even is one. Is there any way to solve this problem (either removing the clutter from code completion开发者_如何学编程, which on it's own doesn't seem likely to be possible, or getting rid of the upfront indices) short of changing the source code and compiling eclipse myself?