To run all tests under valgrind use make test VALGRIND=valgrind, i.e. using memcheck. For helgrind or another tool you need to create a helper script and pass this to the VALGRIND setting.

~/bin/helgrind:
#!/bin/sh
valgrind --tool=helgrind $@

See the helper tools/dev/vgp, tools/dev/vgp_darwin and tools/dev/vgp_old to test single scripts.

There is a Valgrind suppression file at tools/dev/parrot.supp for running Parrot under Valgrind.

General tips for debugging on OS X: http://developer.apple.com/technotes/tn2004/tn2124.html

Use parrot_old, which links to libparrot.a statically. So gdb will resolve all symbols properly.