I tried to install Valgrind with brew install Valgrind and got :
valgrind: This formula either does not compile or function as expected
on macOS
I am having the same issue. It seems like valgrind is not compatible with the newest macOS(10.14 Mojave). Tried installing it the High Sierra way (https://www.gungorbudak.com/blog/2018/04/28/how-to-install-valgrind-on-macos-high-sierra/) and got the same output you described. The only solution I can offer you right now is either working on virtual machine (https://www.virtualbox.org/) or using Docker (https://www.gungorbudak.com/blog/2018/06/13/memory-leak-testing-with-valgrind-on-macos-using-docker-containers/).