I've been drilling deep into MRI's gc.
Does anyone regularly run MRI against valgrind?
I'm seeing quite a few errors on OS X 10.6.6 64-bit.

e.g.:

==36412== Use of uninitialised value of size 8
==36412==    at 0x100054542: mark_current_machine_context (in ./ruby)
==36412==    by 0x10005473A: gc_marks (in ./ruby)
==36412==    by 0x1000558EA: rb_newobj (in ./ruby)
==36412==    by 0x100055E48: rb_node_newnode (in ./ruby)
==36412==    by 0x100099AA4: gettable_gen (in ./ruby)
==36412==    by 0x1000B752E: ruby_yyparse (in ./ruby)
==36412==    by 0x1000B8FC9: yycompile0 (in ./ruby)
==36412==    by 0x10017F7A2: thread_suppress_tracing (in ./ruby)
==36412==    by 0x100096E1F: rb_parser_compile_file (in ./ruby)
==36412==    by 0x1000FBC1B: load_file_internal (in ./ruby)
==36412==    by 0x10003C5CE: rb_ensure (in ./ruby)
==36412==    by 0x1000F950D: rb_load_file (in ./ruby)
==36412==
==36412== Conditional jump or move depends on uninitialised value(s)
==36412==    at 0x100051CAB: gc_mark_children (in ./ruby)
==36412==    by 0x100054622: mark_current_machine_context (in ./ruby)
==36412==    by 0x10005473A: gc_marks (in ./ruby)
==36412==    by 0x1000558EA: rb_newobj (in ./ruby)
==36412==    by 0x100055E48: rb_node_newnode (in ./ruby)
==36412==    by 0x100099AA4: gettable_gen (in ./ruby)
==36412==    by 0x1000B752E: ruby_yyparse (in ./ruby)
==36412==    by 0x1000B8FC9: yycompile0 (in ./ruby)
==36412==    by 0x10017F7A2: thread_suppress_tracing (in ./ruby)
==36412==    by 0x100096E1F: rb_parser_compile_file (in ./ruby)
==36412==    by 0x1000FBC1B: load_file_internal (in ./ruby)
==36412==    by 0x10003C5CE: rb_ensure (in ./ruby)