eina-cxx: Added malloc_clone_allocator to use with POD's when wrapping Eina C structures

Summary:
Added efl::eina::malloc_clone_allocator to be used with ptr_* data
structures for wrapping structures allocated by EFL in C.

This allows for example:

  void foo(Eina_List* l)
  {
    efl::eina::ptr_list<int, efl::eina::malloc_clone_allocator> list(l);
  }

If the standard efl::eina::heap_no_clone_allocator is used, the
deallocation code uses C++ delete operator, which causes undefined
behavior because the allocation was originally done with malloc.

Reviewers: cedric

CC: savio, cedric

Differential Revision: https://phab.enlightenment.org/D614

src/bindings/eina_cxx/eina_clone_allocators.hh

@@ -2,6 +2,9 @@
 #define EINA_CLONE_ALLOCATORS_HH_
 
 #include <memory>
+#include <cstring>
+#include <cstdlib>
+#include <type_traits>
 
 namespace efl { namespace eina {
 
@@ -64,6 +67,25 @@ struct heap_no_copy_allocator
   }
 };    
 
+struct malloc_clone_allocator
+{
+  template <typename T>
+  static T* allocate_clone(T const& v)
+  {
+    static_assert(std::is_pod<T>::value, "malloc_clone_allocator can only be used with POD types");
+    T* p = static_cast<T*>(std::malloc(sizeof(T)));
+    std::memcpy(p, &v, sizeof(T));
+    return p;
+  }
+
+  template <typename T>
+  static void deallocate_clone(T const* p)
+  {
+    static_assert(std::is_pod<T>::value, "malloc_clone_allocator can only be used with POD types");
+    std::free(const_cast<T*>(p));
+  }
+};
+
 } }
 
 #endif

src/tests/eina_cxx/eina_cxx_test_ptrlist.cc

@@ -128,6 +128,19 @@ START_TEST(eina_cxx_ptrlist_insert)
 }
 END_TEST
 
+
+START_TEST(eina_cxx_ptrlist_malloc_clone_allocator)
+{
+  efl::eina::eina_init eina_init;
+
+  efl::eina::ptr_list<int, efl::eina::malloc_clone_allocator> list1;
+  list1.push_back(5);
+  list1.push_back(10);
+
+  efl::eina::ptr_list<int, efl::eina::malloc_clone_allocator> list2 = list1;
+}
+END_TEST
+
 START_TEST(eina_cxx_ptrlist_constructors)
 {
   efl::eina::eina_init eina_init;
@@ -240,4 +253,5 @@ eina_test_ptrlist(TCase* tc)
   tcase_add_test(tc, eina_cxx_ptrlist_constructors);
   tcase_add_test(tc, eina_cxx_ptrlist_erase);
   tcase_add_test(tc, eina_cxx_ptrlist_range);
+  tcase_add_test(tc, eina_cxx_ptrlist_malloc_clone_allocator);
 }