From 107cb48d2f646aaff5f3bd535c532dcc80729dac Mon Sep 17 00:00:00 2001
From: Ryan Curtin <ryan@ratml.org>
Date: Tue, 8 Dec 2020 19:55:27 -0500
Subject: [PATCH] Add finalizers to mlpack objects.

---
 CMake/julia/AppendType.cmake                   | 11 ++++++++++-
 CMake/julia/ConfigureJuliaHCPP.cmake           |  9 +++++++++
 src/mlpack/bindings/julia/print_param_defn.hpp | 18 ++++++++++++++++--
 3 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/CMake/julia/AppendType.cmake b/CMake/julia/AppendType.cmake
index 299be1c6a4..a3b5d2aea6 100644
--- a/CMake/julia/AppendType.cmake
+++ b/CMake/julia/AppendType.cmake
@@ -32,8 +32,17 @@ function(append_type TYPES_FILE PROGRAM_NAME PROGRAM_MAIN_FILE)
         # function.
         file(APPEND
             "${TYPES_FILE}"
-            "struct ${MODEL_SAFE_TYPE}\n"
+            "mutable struct ${MODEL_SAFE_TYPE}\n"
             "  ptr::Ptr{Nothing}\n"
+            "\n"
+            "  # Construct object and set finalizer to free memory.\n"
+            "  function ${MODEL_SAFE_TYPE}(ptr::Ptr{Nothing})::${MODEL_SAFE_TYPE}\n"
+            "    result = new(ptr)\n"
+            "    finalizer(\n"
+            "        x -> _Internal.${PROGRAM_NAME}_internal.Delete${MODEL_SAFE_TYPE}(x.ptr),\n"
+            "        result)\n"
+            "    return result\n"
+            "  end\n"
             "end\n"
             "\n")
       endif ()
diff --git a/CMake/julia/ConfigureJuliaHCPP.cmake b/CMake/julia/ConfigureJuliaHCPP.cmake
index 1fb9a4b4be..38c7be5cbf 100644
--- a/CMake/julia/ConfigureJuliaHCPP.cmake
+++ b/CMake/julia/ConfigureJuliaHCPP.cmake
@@ -29,6 +29,8 @@ if (${NUM_MODEL_TYPES} GREATER 0)
 void* IO_GetParam${MODEL_SAFE_TYPE}Ptr(const char* paramName);
 // Set the pointer to a ${MODEL_TYPE} parameter.
 void IO_SetParam${MODEL_SAFE_TYPE}Ptr(const char* paramName, void* ptr);
+// Delete a ${MODEL_TYPE} pointer.
+void Delete${MODEL_SAFE_TYPE}Ptr(void* ptr);
 // Serialize a ${MODEL_TYPE} pointer.
 char* Serialize${MODEL_SAFE_TYPE}Ptr(void* ptr, size_t* length);
 // Deserialize a ${MODEL_TYPE} pointer.
@@ -50,6 +52,13 @@ void IO_SetParam${MODEL_SAFE_TYPE}Ptr(const char* paramName, void* ptr)
   IO::SetPassed(paramName);
 }
 
+// Delete a ${MODEL_TYPE} pointer.
+void Delete${MODEL_SAFE_TYPE}Ptr(void* ptr)
+{
+  ${MODEL_TYPE}* modelPtr = (${MODEL_TYPE}*) ptr;
+  delete modelPtr;
+}
+
 // Serialize a ${MODEL_TYPE} pointer.
 char* Serialize${MODEL_SAFE_TYPE}Ptr(void* ptr, size_t* length)
 {
diff --git a/src/mlpack/bindings/julia/print_param_defn.hpp b/src/mlpack/bindings/julia/print_param_defn.hpp
index 450b614d5b..51a47d39fd 100644
--- a/src/mlpack/bindings/julia/print_param_defn.hpp
+++ b/src/mlpack/bindings/julia/print_param_defn.hpp
@@ -59,15 +59,20 @@ void PrintParamDefn(
   // import ...<Type>
   //
   // function IOGetParam<Type>(paramName::String)
-  //   <Type>(ccall((:IOGetParam<Type>Ptr, <programName>Library),
+  //   <Type>(ccall((:IO_GetParam<Type>Ptr, <programName>Library),
   //       Ptr{Nothing}, (Cstring,), paramName))
   // end
   //
   // function IOSetParam<Type>(paramName::String, model::<Type>)
-  //   ccall((:IOSetParam<Type>Ptr, <programName>Library), Nothing,
+  //   ccall((:IO_SetParam<Type>Ptr, <programName>Library), Nothing,
   //       (Cstring, Ptr{Nothing}), paramName, model.ptr)
   // end
   //
+  // function Delete<Type>(ptr::Ptr{Nothing})
+  //   ccall((:Delete<Type>Ptr, <programName>Library), Nothing,
+  //       (Ptr{Nothing},), ptr)
+  // end
+  //
   // function serialize<Type>(stream::IO, model::<Type>)
   //   buf_len = UInt[0]
   //   buffer = ccall((:Serialize<Type>Ptr, <programName>Library),
@@ -111,6 +116,15 @@ void PrintParamDefn(
   std::cout << "end" << std::endl;
   std::cout << std::endl;
 
+  // Next, Delete<Type>().
+  std::cout << "# Delete an instantiated model pointer." << std::endl;
+  std::cout << "function Delete" << type << "(ptr::Ptr{Nothing})"
+      << std::endl;
+  std::cout << "  ccall((:Delete" << type << "Ptr, " << programName
+      << "Library), Nothing, (Ptr{Nothing},), ptr)" << std::endl;
+  std::cout << "end" << std::endl;
+  std::cout << std::endl;
+
   // Now the serialization functionality.
   std::cout << "# Serialize a model to the given stream." << std::endl;
   std::cout << "function serialize" << type << "(stream::IO, model::" << type