Hello WebKit folks! I would like to announce that I’ve just landed the patch which introduces `WTF::makeUnique<T>` and `WTF::makeUniqueWithoutFastMallocCheck<T>` in https://trac.webkit.org/changeset/248846 <https://trac.webkit.org/changeset/248846>. They are drop-in-replacement to std::make_unique<T>, and we should not use std::make_unique<T> after that patch is introduced. I’m planning to add cpplint check for `std::make_unique` to avoid the use of that. The motivation behind this change is the following. 1. Our typical way of allocating heap memory is three-fold. Using containers (Vector etc.), RefCounted, and std::unique_ptr. 2. Containers and RefCounted are covered well by FastMalloc. 3. But std::unique_ptr case, we missed using FastMalloc in many places so far. Even in very recently written code, we missed FastMalloc annotation. For example, we sometimes create a data structure just like a struct, and allocate it with make_unique. struct XXXData { ... }; m_data = std::make_unique<XXXData>(); We missed WTF_MAKE_STRUCT_FAST_ALLOCATED annotation in XXXData so frequently so that the allocation of XXXData ends up being allocated from system-malloc. This WTF::makeUnique adds one `static_assert` over std::make_unique: the static_assert ensures T is FastMalloced or IsoHeap-allocated. Otherwise, we see compile-error. This mechanism surprisingly found so many classes that do not have WTF_MAKE_FAST_ALLOCATED / WTF_MAKE_STRUCT_FAST_ALLOCATED in our code base. If the type T comes from ThirdParty and if we cannot annotate T with FAST_ALLOCATED, we can use WTF::makeUniqueWithoutFastMallocCheck explicitly as a fallback. More detailed explanation behind why we took this design (instead of allocating FastMalloced-memory automatically when using makeUnique<T>() etc.) is described in ChangeLog in https://trac.webkit.org/changeset/248846/webkit <https://trac.webkit.org/changeset/248846/webkit>. I already annotated missed structs / classes with WTF_MAKE_FAST_ALLOCATED in https://trac.webkit.org/changeset/248762 <https://trac.webkit.org/changeset/248762>. So, now I think 99% of allocations in WebKit-itself are handled well by FastMalloc. -Yusuke