I heard some time back that Rust folks had stopped using Valgrind/Memcheck to check unsafe Rust, because of false positives resulting from LLVM (correctly) generating branches on undefined values. I've been slowly working to fix this, by making Memcheck able to recover the underlying &&/|| expressions and instrumenting them more accurately.
So I'm looking for Rust folks who might be interested to try out this fixed version and provide feedback. There may be other sources of false positives, but my overall understanding is that we should be able to get close to zero false positives for run-of-the-mill unsafe Rust (and C++), possibly following extra work at this end. The relevant branch is obtained thusly  and a summary of what's changed is at .
 git clone git://sourceware.org/git/valgrind.git ;
cd valgrind ; git checkout grail