[proxy](4/n) use customised placement-new (#719)

* [proxy](4/n) use customized placement-new

* fix

src/snmalloc/mem/corealloc.h

@@ -6,6 +6,7 @@
 #include "pool.h"
 #include "remotecache.h"
 #include "sizeclasstable.h"
+#include "snmalloc/stl/new.h"
 #include "ticker.h"
 
 namespace snmalloc
@@ -1128,7 +1129,8 @@ namespace snmalloc
       capptr::Alloc<void> spare_start = pointer_offset(raw, round_sizeof);
       Range<capptr::bounds::Alloc> r{spare_start, spare};
 
-      auto p = capptr::Alloc<CA>::unsafe_from(new (raw.unsafe_ptr()) CA(r));
+      auto p = capptr::Alloc<CA>::unsafe_from(
+        new (raw.unsafe_ptr(), placement_token) CA(r));
 
       // Remove excess from the bounds.
       p = Aal::capptr_bound<CA, capptr::bounds::Alloc>(p, round_sizeof);

src/snmalloc/mem/freelist.h

@@ -35,6 +35,7 @@
 
 #include "../ds/ds.h"
 #include "entropy.h"
+#include "snmalloc/stl/new.h"
 
 #include <cstdint>
 
@@ -265,7 +266,7 @@ namespace snmalloc
       static BHeadPtr<BView, BQueue> make(CapPtr<void, BView> p)
       {
         return CapPtr<Object::T<BQueue>, BView>::unsafe_from(
-          new (p.unsafe_ptr()) Object::T());
+          new (p.unsafe_ptr(), placement_token) Object::T());
       }
 
       /**

src/snmalloc/mem/metadata.h

@@ -3,6 +3,7 @@
 #include "../ds/ds.h"
 #include "freelist.h"
 #include "sizeclasstable.h"
+#include "snmalloc/stl/new.h"
 
 namespace snmalloc
 {
@@ -466,7 +467,7 @@ namespace snmalloc
 
       large_ = false;
 
-      new (&client_meta_)
+      new (&client_meta_, placement_token)
         typename ClientMeta::StorageType[get_client_storage_count(sizeclass)];
     }
 
@@ -486,7 +487,7 @@ namespace snmalloc
       // Jump to slow path on first deallocation.
       needed() = 1;
 
-      new (&client_meta_) typename ClientMeta::StorageType();
+      new (&client_meta_, placement_token) typename ClientMeta::StorageType();
     }
 
     /**

src/snmalloc/mem/pool.h

@@ -3,8 +3,6 @@
 #include "../ds/ds.h"
 #include "pooled.h"
 
-#include <new>
-
 namespace snmalloc
 {
   /**

src/snmalloc/mem/remoteallocator.h

@@ -1,8 +1,7 @@
 #pragma once
 
 #include "freelist_queue.h"
-
+#include "snmalloc/stl/new.h"
-#include <new>
 
 namespace snmalloc
 {
@@ -43,7 +42,7 @@ namespace snmalloc
     static auto emplace_in_alloc(capptr::Alloc<void> alloc)
     {
       return CapPtr<BatchedRemoteMessage, capptr::bounds::Alloc>::unsafe_from(
-        new (alloc.unsafe_ptr()) BatchedRemoteMessage());
+        new (alloc.unsafe_ptr(), placement_token) BatchedRemoteMessage());
     }
 
     static auto mk_from_freelist_builder(
@@ -67,7 +66,7 @@ namespace snmalloc
       auto last_prev = last->prev;
       auto self =
         CapPtr<BatchedRemoteMessage, capptr::bounds::Alloc>::unsafe_from(
-          new (last.unsafe_ptr()) BatchedRemoteMessage());
+          new (last.unsafe_ptr(), placement_token) BatchedRemoteMessage());
       self->free_ring.prev = last_prev;
 
       // XXX On CHERI, we could do a fair bit better if we had a primitive for
@@ -222,7 +221,7 @@ namespace snmalloc
     static auto emplace_in_alloc(capptr::Alloc<void> alloc)
     {
       return CapPtr<SingletonRemoteMessage, capptr::bounds::Alloc>::unsafe_from(
-        new (alloc.unsafe_ptr()) SingletonRemoteMessage());
+        new (alloc.unsafe_ptr(), placement_token) SingletonRemoteMessage());
     }
 
     static freelist::HeadPtr

src/snmalloc/stl/new.h

@@ -0,0 +1,35 @@
+#pragma once
+
+#include "snmalloc/ds_core/defines.h"
+
+namespace snmalloc
+{
+
+  // This is used in both vendored and non-vendored mode.
+  struct PlacementToken
+  {};
+
+  inline constexpr PlacementToken placement_token{};
+} // namespace snmalloc
+
+SNMALLOC_FAST_PATH_INLINE void*
+operator new(size_t, void* ptr, snmalloc::PlacementToken) noexcept
+{
+  return ptr;
+}
+
+SNMALLOC_FAST_PATH_INLINE void*
+operator new[](size_t, void* ptr, snmalloc::PlacementToken) noexcept
+{
+  return ptr;
+}
+
+// The following is not really needed, but windows expects that new/delete
+// definitions are paired.
+SNMALLOC_FAST_PATH_INLINE void
+operator delete(void*, void*, snmalloc::PlacementToken) noexcept
+{}
+
+SNMALLOC_FAST_PATH_INLINE void
+operator delete[](void*, void*, snmalloc::PlacementToken) noexcept
+{}