Testing libc++ with Address Sanitizer

[This article is re-posted in a slightly expanded form from Marshall's blog]
I've been running the libc++ tests off and on for a while. It's a quite extensive test suite, but I wondered if there were any bugs that the test suite was not uncovering. In the upcoming clang 3.3, there is a new feature named Address Sanitizer which inserts a bunch of runtime checks into your executable to see if there are any "out of bounds" reads and writes to memory.
In the back of my head, I've always thought that it would be nice to be able to say that libc++ was "ASan clean" (i.e, passed all of the test suite when running with Address Sanitizer).
So I decided to do that.

Instruction Relationship Framework in LLVM

The article provides an overview of the new Relationship framework of TableGen. This TableGen feature is used to describe user defined relationships between instructions. It was added to LLVM in October 2012.