Ensure the container node size is always properly aligned for pointers

Fixes #171.

Author: foonathan

cmake/get_container_node_sizes.cmake

@@ -181,7 +181,7 @@ namespace detail
 template <typename T>
 struct ${container}_node_size
 : std::integral_constant<std::size_t,
-       detail::${container}_node_size<alignof(T)>::value + sizeof(T)>
+    detail::round_up_to_multiple_of_alignment(detail::${container}_node_size<alignof(T)>::value + sizeof(T), alignof(void*))>
 {};
 ")
     endforeach()

include/foonathan/memory/detail/align.hpp

@@ -21,6 +21,13 @@ namespace foonathan
                 return alignment && (alignment & (alignment - 1)) == 0u;
             }
 
+            constexpr std::size_t round_up_to_multiple_of_alignment(std::size_t size,
+                                                                    std::size_t alignment) noexcept
+            {
+                FOONATHAN_MEMORY_ASSERT(is_valid_alignment(alignment));
+                return (size + alignment - 1) & ~(alignment - 1);
+            }
+
             // returns the offset needed to align ptr for given alignment
             // alignment must be valid
             inline std::size_t align_offset(std::uintptr_t address, std::size_t alignment) noexcept
@@ -45,7 +52,7 @@ namespace foonathan
             // returns the minimum alignment required for a node of given size
             std::size_t alignment_for(std::size_t size) noexcept;
         } // namespace detail
-    }     // namespace memory
+    } // namespace memory
 } // namespace foonathan
 
 #endif // FOONATHAN_MEMORY_DETAIL_ALIGN_HPP_INCLUDED

include/foonathan/memory/detail/container_node_sizes.hpp

@@ -4,6 +4,7 @@
 #ifndef FOONATHAN_MEMORY_DETAIL_CONTAINER_NODE_SIZES_HPP_INCLUDED
 #define FOONATHAN_MEMORY_DETAIL_CONTAINER_NODE_SIZES_HPP_INCLUDED
 
+#include "align.hpp"
 #include "container_node_sizes_impl.hpp"
 
 #endif //FOONATHAN_MEMORY_DETAIL_CONTAINER_NODE_SIZES_HPP_INCLUDED

test/detail/align.cpp

@@ -8,6 +8,21 @@
 using namespace foonathan::memory;
 using namespace detail;
 
+TEST_CASE("detail::round_up_to_multiple_of_alignment")
+{
+    REQUIRE(round_up_to_multiple_of_alignment(0, 1) == 0);
+    REQUIRE(round_up_to_multiple_of_alignment(1, 1) == 1);
+    REQUIRE(round_up_to_multiple_of_alignment(2, 1) == 2);
+    REQUIRE(round_up_to_multiple_of_alignment(3, 1) == 3);
+    REQUIRE(round_up_to_multiple_of_alignment(4, 1) == 4);
+
+    REQUIRE(round_up_to_multiple_of_alignment(0, 2) == 0);
+    REQUIRE(round_up_to_multiple_of_alignment(1, 2) == 2);
+    REQUIRE(round_up_to_multiple_of_alignment(2, 2) == 2);
+    REQUIRE(round_up_to_multiple_of_alignment(3, 2) == 4);
+    REQUIRE(round_up_to_multiple_of_alignment(4, 2) == 4);
+}
+
 TEST_CASE("detail::align_offset")
 {
     auto ptr = reinterpret_cast<void*>(0);

tool/node_size_debugger.cpp

@@ -91,8 +91,9 @@ struct code_serializer
         out << "} // namespace detail" << newline << newline << "template <typename T>" << newline
             << "struct " << struct_name(result.container_name) << newline
             << ": std::integral_constant<std::size_t," << newline
-            << "       detail::" << struct_name(result.container_name) << '<' << alignment
-            << ">::value + sizeof(T)>" << newline << "{};" << newline << newline;
+            << "       detail::round_up_to_multiple_of_alignment(detail::"
+            << struct_name(result.container_name) << '<' << alignment
+            << ">::value + sizeof(T), alignof(void*))>" << newline << "{};" << newline << newline;
     }
 
     void suffix() const