With next month's release of LLVM 3.3 quickly approaching, here's an overview of some of the best and most exciting features coming to this next major update of the LLVM compiler infrastructure and Clang C/C++ compiler front-end...
What is the difference between "feature complete" and "effectively feature complete"?
Some corner cases, optional specs, or inapplicable features may be missing. Some of the C++11 bits are also part of the library, not language, and so conformance relies on libstdc++ to provide. Really for all practical purposes it's complete, though. From my understanding the only "missing" bits in GCC are missing in Clang, too, but the Clang developers were more upfront in just declaring those features N/A to Clang or explaining why they weren't ever going to implement them. It's hard to directly compare the feature status pages of GCC and Clang because they don't necessarily agree on how to label a particular feature. GCC lists for extended integral types "Yes" while Clang says "No" with a footnote explaining how they (just like GCC) cannot fully implement the feature for ABI reasons.
Of course, this is all moot now, since they're both basically full C++11 compilers. Now the race is on for C++14/17, with both compilers coming out ahead in different ways (although Clang has an edge if you look at branches/forks; it's more frequently being used a testbed for language proposals due likely to how much easier it is to extend and experiment with).