The rationale for the move is
- sanitizer_internal_defs.h is included from asan_dll_thunk.cc, which expects only the minimal amount of declarations. Leaving the __sanitizer functions in sanitizer_internal_defs.h results in extra maintenance cost of asan_dll_thunk.cc (see INTERFACE_FUNCTION macro)
- According to the top comment, sanitizer_internal_defs.h is supposed to "contain macro used in run-time libraries code." Clearly, the __sanitizer_* function definitions are not macros. Also, they don't have to be declared in all our TUs.
I'm assigning you to the review as you've added the __sanitizer interface into sanitizer_internal_defs.h in http://llvm.org/viewvc/llvm-project?revision=173928&view=revision