Well... it looks like Krzysztof found us a nice, tricky problem in regards to the whole hash_map/unordered_list mess. What he has been tripped up by is one of those ugly problems with no simple solutions.
First, we have legacy code that is using a gcc extension. Not so good. Next the replacement has problems on many systems. So we don't have a tidy solution.
General questions for any thing with warnings, etc.
* Are the warnings critical? That is, do they indicate some immediate risk/failure? If so, then we should address them sooner
* Do we need to be using it? That is, are there any alternatives to the code creating warnings? Things such as vector instead of list, map instead of hash_map, etc.
* Can we encapsulate it? That is, do we need to leave things in .h files that other things include, or can they be moved inside specific files?
* Is there a clean way to fix at least some of the warnings? For some, this may be as simple as using an explicit variable instead of a temporary. In this case there appears not to be
* Is it cross-platform? Remember, we need to keep Inkscape compatible with multiple platforms, including MS Windows, Linux, OS X, BSD, Solaris, etc.
I'll try to follow up on a few of these points.