The last time I tried using mach clang-format, I ran into bug 983633. Since that has been fixed, I'm trying it again (albeit with some delay). This is what happens: kats@kgupta-air src$ mach clang-format filterdiff(63655,0x7fff719f5310) malloc: *** error for object 0x7fff511b69a0: pointer being realloc'd was not allocated *** set a breakpoint in malloc_error_break to debug Running on OS X 10.9.2 on a clean m-c tree. For the record, I really just want a tool that will reformat an entire file using the mozilla style guide, not something that operates on diffs.
Looks like filterdiff is broken on your Mac. You'll need to find someone who speaks Mac to sort that out. To format a whole file you can run: $ ~/.mozbuild/clang-format-3.5 -i MyFile.cpp
Since filterdiff came from brew it's not really a mozilla problem. Closing this bug as invalid. Thanks for the pointer to clang-format -i.
FYI, this is a filterdiff bug. I've created a ticket in patchutil Trac.  https://fedorahosted.org/patchutils/ticket/30
I've applied John's patch to homebrew's patchutils. The filterdiff crash should be fixed after patchutils is reinstalled. https://github.com/Homebrew/homebrew/commit/9062ea239de127b9bd6202bf2e4da7a22ba9e29d