Google's Diego Novillo has shared that a new transitional branch has been made in the process of porting ASAN to trunk. "I have created a temporary branch to host the port of ASAN to trunk. Wei has done the initial port of the original code from Kostya. It compiles but we still do not have the runtimes (Wei is working on that)."
ASAN is the AddressSanitizer that serves as a memory error detector for C and C++ codes. AddressSanitizer is capable of detecting memory bugs such as use-after-free, heap buffer overflows, stack buffer overflows, global buffer overflows, and use-after-return. One of the benefits of AddressSanitizer over alternatives like Valgrind is that ASAN is designed to be very fast. AddressSanitizer within LLVM/Clang serves as a compiler instrumentation module in the form of an LLVM pass and then a run-time library that overrides the memory allocation functions.
Running AddressSanitizer binaries lead to a reported slowdown of about 2x, which is still faster than similar memory checking tools. GNU Compiler Collection developers have been interested in AddressSanitizer support and there's been some work previously while now it seems to finally be coming together with this transitional branch as the current code is made compatible with the latest GCC trunk, which is needed before it can be merged.
The GCC ASAN run-time also then needs to be written before it's actually useful, but Diego mentions that it should come soon.
More information on AddressSanitizer (ASAN) is available from its Google Code page.