message: meshable-arena: more info in debugging asserts
diff: @@ -218,7 +218,8 @@ void *MeshableArena::malloc(size_t sz) {
  auto span = reservePages(pageCount);
  const auto off = span.offset;
  - d_assert(getMetadataFlags(off) == 0 && getMetadataPtr(off) == 0);
  + d_assert(span.ptr(_arenaBegin) < arenaEnd());
  + d_assert_msg(getMetadataFlags(off) == 0 && getMetadataPtr(off) == 0, "expected no metadata, found %p/%zu", getMetadataPtr(off), getMetadataFlags(off));
  // now that we know they are available, set the empty pages to
  // in-use. This is safe because this whole function is called
  