Clean up allocator TODOs and add max_size

Author: jslee02

dart/common/MemoryAllocator.hpp

@@ -69,7 +69,7 @@ class DART_API MemoryAllocator : public Castable<MemoryAllocator>
   /// memory.
   /// @return On failure, a null pointer
   [[nodiscard]] virtual void* allocate(size_t bytes) noexcept = 0;
-  // TODO(JS): Make this constexpr once migrated to C++20
+  // Note: Virtual runtime allocation cannot be constexpr by design.
 
   /// Allocates object(s) without calling the constructor.
   ///
@@ -85,7 +85,7 @@ class DART_API MemoryAllocator : public Castable<MemoryAllocator>
   /// @param[in] pointer: Pointer obtained from allocate().
   /// @param[in] bytes: The bytes of the allocated memory.
   virtual void deallocate(void* pointer, size_t bytes) = 0;
-  // TODO(JS): Make this constexpr once migrated to C++20
+  // Note: Virtual runtime deallocation cannot be constexpr by design.
 
   /// Allocates uninitialized storage and constructs an object of type T to the
   /// allocated storage.

dart/common/MemoryManager.hpp

@@ -110,7 +110,7 @@ class DART_API MemoryManager final
   /// @param[in] pointer: Pointer obtained from allocate().
   /// @param[in] bytes: The bytes of the allocated memory.
   void deallocate(Type type, void* pointer, size_t bytes);
-  // TODO(JS): Make this constexpr once migrated to C++20
+  // Note: Deallocates runtime memory; constexpr is not applicable.
 
   void deallocateUsingFree(void* pointer, size_t bytes);
 

dart/common/StlAllocator.hpp

@@ -85,10 +85,13 @@ class StlAllocator : public std::allocator<T>
   ///
   /// @param[in] pointer: Pointer obtained from allocate().
   /// @param[in] n: Number of objects earlier passed to allocate().
-  void deallocate(pointer pointer, size_type n);
-  // TODO(JS): Make this constexpr once migrated to C++20
+  void deallocate(pointer pointer, size_type n) noexcept;
 
-  // TODO(JS): Add size_type max_size() const noexcept;
+  /// Upper bound on elements that can be allocated.
+  [[nodiscard]] constexpr size_type max_size() const noexcept
+  {
+    return std::allocator_traits<Base>::max_size(*this);
+  }
 
   /// Prints state of the memory allocator
   void print(std::ostream& os = std::cout, int indent = 0) const;

dart/common/detail/StlAllocator-impl.hpp

@@ -80,7 +80,7 @@ typename StlAllocator<T>::pointer StlAllocator<T>::allocate(
 
 //==============================================================================
 template <typename T>
-void StlAllocator<T>::deallocate(pointer pointer, size_type n)
+void StlAllocator<T>::deallocate(pointer pointer, size_type n) noexcept
 {
   mBaseAllocator.deallocate(pointer, n * sizeof(T));
 }

examples/heightmap/main.cpp

@@ -92,7 +92,6 @@ dynamics::SimpleFramePtr createHeightmapFrame(
 
   terrainFrame->createVisualAspect();
 
-  // TODO(JS): Remove?
   auto terrainShape = createHeightmapShape(
       xResolution, yResolution, xSize, ySize, zMin, zMax);
   terrainFrame->setShape(terrainShape);