CPUPROFILE_OBJECTS causes segfault

[IdahoEv]

I'm trying to profile a bunch of specs in two projects (to figure out why very similar spec suites take 3 minutes in one project and 30 in the other). setting CPUPROFILE_OBJECTS=1 is causing a segfault with each attempt. Segfault occurs after the spec run completes; I see normal spec output first.

System: OS X 10.7.5 Lion
Ruby:
1.9.3-p385
1.9.3-p327-fast (patched GC)

The stack trace / segfault info is nearly 3000 lines, and the crash report in ~/Library/Logs/CrashReporter is 220. Do you want any particular part of it? Possibly relevant snippets are below.

Here's the top of the crash log:

Exception Type:  EXC_BAD_ACCESS (SIGABRT)
Exception Codes: KERN_PROTECTION_FAILURE at 0x00007fc1089c2a68

VM Regions Near 0x7fc1089c2a68:
MALLOC_TINY            00007fc107400000-00007fc107700000 [ 3072K] rw-/rwx SM=COW  
--> MALLOC_SMALL           00007fc107800000-00007fc10a000000 [ 40.0M] rw-/rwx SM=PRV  
MALLOC_TINY            00007fc10a000000-00007fc10a800000 [ 8192K] rw-/rwx SM=PRV  

And the top of the control frame from the segfault:

c:0074 p:---- s:0272 b:0272 l:000267 d:000271 IFUNC
c:0073 p:---- s:0270 b:0270 l:000269 d:000269 CFUNC  :each
c:0072 p:---- s:0268 b:0268 l:000267 d:000267 CFUNC  :group_by
c:0071 p:0014 s:0265 b:0265 l:000264 d:000264 METHOD /Volumes/Valinor/Users/evan/.rvm/gems/ruby-1.9.3-p385/gems/backports-2.6.7/lib/backports/tools.rb:29