Function exception_begin_llvm_ptr

src/exception_headers.h:27–32

};

static cxa_exception_begin_llvm* exception_begin_llvm_ptr(void* ptr) {
  size_t kExceptionBeginOffset = (
    sizeof(void*) == 8 ? 128 : 80
  );
  return (cxa_exception_begin_llvm*)((char*)ptr - kExceptionBeginOffset);
}

// https://github.com/gcc-mirror/gcc/blob/5d2a360f0a541646abb11efdbabc33c6a04de7ee/libstdc%2B%2B-v3/libsupc%2B%2B/unwind-cxx.h#L100
struct cxa_exception_begin_gcc {