add include cstdef for std::size_t in C++
@@ -388,6 +388,7 @@ mi_decl_nodiscard mi_decl_export void* mi_new_reallocn(void* p, size_t newcount,
// ---------------------------------------------------------------------------------------------
#ifdef __cplusplus
+#include <cstddef> // std::size_t
#include <cstdint> // PTRDIFF_MAX
#if (__cplusplus >= 201103L) || (_MSC_VER > 1900) // C++11
#include <type_traits> // std::true_type
