libstdc++: Make pmr::memory_resource::allocate implicitly create objects

Calling the placement version of ::operator new "implicitly creates
objects in the returned region of storage" as per [intro.object]. This
allows the returned memory to be used as storage for implicit-lifetime
types (including arrays) without additional action by the caller. This
is required by the proposed resolution of LWG 3147.

libstdc++-v3/ChangeLog:

	* include/std/memory_resource (memory_resource::allocate):
	Implicitly create objects in the returned storage.

diff --git a/libstdc++-v3/include/std/memory_resource b/libstdc++-v3/include/std/memory_resource
index 6bca0afa018074ba747fc0b4eb3699afbc615920..97d37f18512b97420738988972a10b4afcfccf90 100644 (file)
--- a/libstdc++-v3/include/std/memory_resource
+++ b/libstdc++-v3/include/std/memory_resource
@@ -33,6 +33,7 @@
 
 #if __cplusplus >= 201703L
 
+#include <new>
 #include <vector>                      // vector
 #include <cstddef>                     // size_t, max_align_t, byte
 #include <shared_mutex>                        // shared_mutex
@@ -103,7 +104,7 @@ namespace pmr
     void*
     allocate(size_t __bytes, size_t __alignment = _S_max_align)
     __attribute__((__returns_nonnull__,__alloc_size__(2),__alloc_align__(3)))
-    { return do_allocate(__bytes, __alignment); }
+    { return ::operator new(__bytes, do_allocate(__bytes, __alignment)); }
 
     void
     deallocate(void* __p, size_t __bytes, size_t __alignment = _S_max_align)