Function __cxa_allocate_exception

src/from_exception.cpp:232–275

}

extern "C" BOOST_SYMBOL_EXPORT
void* __cxa_allocate_exception(size_t thrown_size) throw() {
  static const auto orig_allocate_exception = []() {
    void* const ptr = ::dlsym(RTLD_NEXT, "__cxa_allocate_exception");
    BOOST_ASSERT_MSG(ptr, "Failed to find '__cxa_allocate_exception'");
    return reinterpret_cast<void*(*)(size_t)>(ptr);
  }();

  if (!boost::stacktrace::impl::ref_capture_stacktraces_at_throw()) {
    return orig_allocate_exception(thrown_size);
  }

#ifndef NDEBUG
  static thread_local std::size_t in_allocate_exception = 0;
  BOOST_ASSERT_MSG(in_allocate_exception < 10, "Suspicious recursion");
  ++in_allocate_exception;
  const decrement_on_destroy guard{in_allocate_exception};
#endif

  static constexpr std::size_t kAlign = alignof(std::max_align_t);
  thrown_size = (thrown_size + kAlign - 1) & (~(kAlign - 1));

  void* const ptr = orig_allocate_exception(thrown_size + kStacktraceDumpSize);
  char* const dump_ptr = static_cast<char*>(ptr) + thrown_size;

  constexpr size_t kSkip = 1;
  boost::stacktrace::safe_dump_to(kSkip, dump_ptr, kStacktraceDumpSize);

#if !BOOST_STACKTRACE_ALWAYS_STORE_IN_PADDING
  if (is_libcpp_runtime()) {
    const std::lock_guard<std::mutex> guard{g_mapping_mutex};
    g_exception_to_dump_mapping[ptr] = dump_ptr;
  } else
#endif
  {
    BOOST_ASSERT_MSG(
      reference_to_empty_padding(ptr) == nullptr,
      "Not zeroed out, unsupported implementation"
    );
    reference_to_empty_padding(ptr) = dump_ptr;
  }

  return ptr;
}

#if !BOOST_STACKTRACE_ALWAYS_STORE_IN_PADDING