You mean Sierra / High Sierra. This is because of compatibility breaking changes to some low-level kernel system calls. Since valgrind is essentially a CPU emu

You mean Sierra / High Sierra. This is because of compatibility breaking changes to some low-level kernel system calls. Since valgrind is essentially a CPU emulator, it is tightly integrated with the OS kernel, and has to be updated accordingly. The macOS contributors to valgrind seem to be relatively few, probably because most macOS developers primarily use the various sanitisers in clang (they also have UI integration in Xcode). Have you tried the clang or gcc asan/tsan/usan sanitisers as a replacment? There are pros and cons of valgrind vs compile time instrumentation. The sanitisers increase the memory footprint, but run with less overhead. valgrind can detect some errors that the sanitizers cannot etc.