Facebook is considering open sourcing at least one of its C++ libraries. The little kernel of news is buried in a Server-Side Magazine interview with Facebook research engineer Andrei Alexandrescu, who works on Facebook's core C++ library. Here's the relevant excerpt that I found (truthfully, the whole interview is worth reading, so go check it out):
This year may also see the launch of some of Facebook's core C++ library code. We're quite excited about that; there is some really cool stuff in there, most of which is directly aimed at high-performance server-side computing. Definitely something to watch for.
Facebook uses C++ heavily on its back-end systems. This is for performance reasons, but of course there are drawbacks as well, such as compilation times. If the C++ code is open-sourced, it could be quite useful. After all, Facebook obviously cares more about its back-end than its front-end, which means its C++ code must be pristine, at least when compared to its PHP code.
If you want to learn even more about how Facebook uses C++, you should also read "HipHop for PHP: Move Fast" on Facebook Developers:
HipHop for PHP isn't technically a compiler itself. Rather it is a source code transformer. HipHop programmatically transforms your PHP source code into highly optimized C++ and then uses g++ to compile it. HipHop executes the source code in a semantically equivalent manner and sacrifices some rarely used features — such as eval() — in exchange for improved performance. HipHop includes a code transformer, a reimplementation of PHP's runtime system, and a rewrite of many common PHP Extensions to take advantage of these performance optimizations.
I don't pretend to understand it all, but I can definitely appreciate that Facebook is trying to explain it to anyone who wants to read it.
C++ and PHP have their own Facebook Pages, with over 73,000 Likes and 218,000 Likes, respectively.