Yosemite and Valgrind
Solution 1:
As there's no stable release that supports Yosemite, you can install the latest development version with
brew install --HEAD valgrind
Solution 2:
Whilst it may have been the case in past OS X release cycles that Valgrind took a period of time before achieving reasonable feature support, basic OS X 10.10 support is already available in Valgrind trunk due to significant work on pre-release Yosemite.
From the mailing list:
There has been some effort recently to improve Valgrind's support for Yosemite. If you develop on Mac OS, you might like to try out the trunk (svn co svn://svn.valgrind.org/valgrind/trunk) and report any breakage you get. Support for Yosemite is good enough that at least one large graphical application (Firefox) runs OK. Support for the previous release, 10.9 (Mavericks), is also substantially improved.
Note that the work has targetted 64 bit processes only. 32 bit might work, and probably better on Mavericks, but I suspect it will be increasingly problematic on Yosemite due to Valgrind's 32 bit x86 instruction set support not having progressed passed SSSE3.
Julian Seward
http://sourceforge.net/p/valgrind/mailman/message/33047840/
Full disclosure: I'm one of the new Valgrind developers who contributed patches to support OS X 10.10