[R-package] move more finalizer logic into C++ side to address memory leaks

R-package/R/lgb.Booster.R

@@ -11,21 +11,12 @@ Booster <- R6::R6Class(
 
     # Finalize will free up the handles
     finalize = function() {
-
-      # Check the need for freeing handle
-      if (!lgb.is.null.handle(x = private$handle)) {
-
-        # Freeing up handle
-        .Call(
-          LGBM_BoosterFree_R
-          , private$handle
-        )
-        private$handle <- NULL
-
-      }
-
+      .Call(
+        LGBM_BoosterFree_R
+        , private$handle
+      )
+      private$handle <- NULL
       return(invisible(NULL))
-
     },
 
     # Initialize will create a starter booster

R-package/R/lgb.Dataset.R

@@ -8,21 +8,12 @@ Dataset <- R6::R6Class(
 
     # Finalize will free up the handles
     finalize = function() {
-
-      # Check the need for freeing handle
-      if (!lgb.is.null.handle(x = private$handle)) {
-
-        # Freeing up handle
-        .Call(
-          LGBM_DatasetFree_R
-          , private$handle
-        )
-        private$handle <- NULL
-
-      }
-
+      .Call(
+        LGBM_DatasetFree_R
+        , private$handle
+      )
+      private$handle <- NULL
       return(invisible(NULL))
-
     },
 
     # Initialize will create a starter dataset

R-package/R/lgb.Predictor.R

@@ -11,9 +11,8 @@ Predictor <- R6::R6Class(
     finalize = function() {
 
       # Check the need for freeing handle
-      if (private$need_free_handle && !lgb.is.null.handle(x = private$handle)) {
+      if (private$need_free_handle) {
 
-        # Freeing up handle
         .Call(
           LGBM_BoosterFree_R
           , private$handle

R-package/src/lightgbm_R.cpp

@@ -46,6 +46,10 @@ SEXP LGBM_HandleIsNull_R(SEXP handle) {
   return Rf_ScalarLogical(R_ExternalPtrAddr(handle) == NULL);
 }
 
+void _DatasetFinalizer(SEXP handle) {
+  LGBM_DatasetFree_R(handle);
+}
+
 SEXP LGBM_DatasetCreateFromFile_R(SEXP filename,
   SEXP parameters,
   SEXP reference) {
@@ -59,6 +63,7 @@ SEXP LGBM_DatasetCreateFromFile_R(SEXP filename,
   CHECK_CALL(LGBM_DatasetCreateFromFile(CHAR(Rf_asChar(filename)), CHAR(Rf_asChar(parameters)),
     ref, &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _DatasetFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -90,6 +95,7 @@ SEXP LGBM_DatasetCreateFromCSC_R(SEXP indptr,
     p_data, C_API_DTYPE_FLOAT64, nindptr, ndata,
     nrow, CHAR(Rf_asChar(parameters)), ref, &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _DatasetFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -113,6 +119,7 @@ SEXP LGBM_DatasetCreateFromMat_R(SEXP data,
   CHECK_CALL(LGBM_DatasetCreateFromMat(p_mat, C_API_DTYPE_FLOAT64, nrow, ncol, COL_MAJOR,
     CHAR(Rf_asChar(parameters)), ref, &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _DatasetFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -136,6 +143,7 @@ SEXP LGBM_DatasetGetSubset_R(SEXP handle,
     idxvec.data(), len, CHAR(Rf_asChar(parameters)),
     &res));
   ret = PROTECT(R_MakeExternalPtr(res, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _DatasetFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -211,7 +219,7 @@ SEXP LGBM_DatasetSaveBinary_R(SEXP handle,
 
 SEXP LGBM_DatasetFree_R(SEXP handle) {
   R_API_BEGIN();
-  if (R_ExternalPtrAddr(handle)) {
+  if (!Rf_isNull(handle) && R_ExternalPtrAddr(handle)) {
     CHECK_CALL(LGBM_DatasetFree(R_ExternalPtrAddr(handle)));
     R_ClearExternalPtr(handle);
   }
@@ -320,9 +328,13 @@ SEXP LGBM_DatasetGetNumFeature_R(SEXP handle,
 
 // --- start Booster interfaces
 
+void _BoosterFinalizer(SEXP handle) {
+  LGBM_BoosterFree_R(handle);
+}
+
 SEXP LGBM_BoosterFree_R(SEXP handle) {
   R_API_BEGIN();
-  if (R_ExternalPtrAddr(handle)) {
+  if (!Rf_isNull(handle) && R_ExternalPtrAddr(handle)) {
     CHECK_CALL(LGBM_BoosterFree(R_ExternalPtrAddr(handle)));
     R_ClearExternalPtr(handle);
   }
@@ -336,6 +348,7 @@ SEXP LGBM_BoosterCreate_R(SEXP train_data,
   BoosterHandle handle = nullptr;
   CHECK_CALL(LGBM_BoosterCreate(R_ExternalPtrAddr(train_data), CHAR(Rf_asChar(parameters)), &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _BoosterFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -348,6 +361,7 @@ SEXP LGBM_BoosterCreateFromModelfile_R(SEXP filename) {
   BoosterHandle handle = nullptr;
   CHECK_CALL(LGBM_BoosterCreateFromModelfile(CHAR(Rf_asChar(filename)), &out_num_iterations, &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _BoosterFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();
@@ -360,6 +374,7 @@ SEXP LGBM_BoosterLoadModelFromString_R(SEXP model_str) {
   BoosterHandle handle = nullptr;
   CHECK_CALL(LGBM_BoosterLoadModelFromString(CHAR(Rf_asChar(model_str)), &out_num_iterations, &handle));
   ret = PROTECT(R_MakeExternalPtr(handle, R_NilValue, R_NilValue));
+  R_RegisterCFinalizerEx(ret, _BoosterFinalizer, TRUE);
   UNPROTECT(1);
   return ret;
   R_API_END();

R-package/tests/testthat/test_Predictor.R

@@ -1,5 +1,31 @@
 context("Predictor")
 
+test_that("Predictor$finalize() should not fail", {
+    X <- as.matrix(as.integer(iris[, "Species"]), ncol = 1L)
+    y <- iris[["Sepal.Length"]]
+    dtrain <- lgb.Dataset(X, label = y)
+    bst <- lgb.train(
+        data = dtrain
+        , objective = "regression"
+        , verbose = -1L
+        , nrounds = 3L
+    )
+    model_file <- tempfile(fileext = ".model")
+    bst$save_model(filename = model_file)
+    predictor <- Predictor$new(modelfile = model_file)
+
+    expect_true(lgb.is.Predictor(predictor))
+
+    expect_false(lgb.is.null.handle(predictor$.__enclos_env__$private$handle))
+
+    predictor$finalize()
+    expect_true(lgb.is.null.handle(predictor$.__enclos_env__$private$handle))
+
+    # calling finalize() a second time shouldn't cause any issues
+    predictor$finalize()
+    expect_true(lgb.is.null.handle(predictor$.__enclos_env__$private$handle))
+})
+
 test_that("predictions do not fail for integer input", {
     X <- as.matrix(as.integer(iris[, "Species"]), ncol = 1L)
     y <- iris[["Sepal.Length"]]

R-package/tests/testthat/test_dataset.R

@@ -215,6 +215,24 @@ test_that("Dataset$update_params() works correctly for recognized Dataset parame
   }
 })
 
+test_that("Dataset$finalize() should not fail on an already-finalized Dataset", {
+  dtest <- lgb.Dataset(
+    data = test_data
+    , label = test_label
+  )
+  expect_true(lgb.is.null.handle(dtest$.__enclos_env__$private$handle))
+
+  dtest$construct()
+  expect_false(lgb.is.null.handle(dtest$.__enclos_env__$private$handle))
+
+  dtest$finalize()
+  expect_true(lgb.is.null.handle(dtest$.__enclos_env__$private$handle))
+
+  # calling finalize() a second time shouldn't cause any issues
+  dtest$finalize()
+  expect_true(lgb.is.null.handle(dtest$.__enclos_env__$private$handle))
+})
+
 test_that("lgb.Dataset: should be able to run lgb.train() immediately after using lgb.Dataset() on a file", {
   dtest <- lgb.Dataset(
     data = test_data

R-package/tests/testthat/test_lgb.Booster.R

@@ -1,3 +1,27 @@
+context("Booster")
+
+test_that("Booster$finalize() should not fail", {
+    X <- as.matrix(as.integer(iris[, "Species"]), ncol = 1L)
+    y <- iris[["Sepal.Length"]]
+    dtrain <- lgb.Dataset(X, label = y)
+    bst <- lgb.train(
+        data = dtrain
+        , objective = "regression"
+        , verbose = -1L
+        , nrounds = 3L
+    )
+    expect_true(lgb.is.Booster(bst))
+
+    expect_false(lgb.is.null.handle(bst$.__enclos_env__$private$handle))
+
+    bst$finalize()
+    expect_true(lgb.is.null.handle(bst$.__enclos_env__$private$handle))
+
+    # calling finalize() a second time shouldn't cause any issues
+    bst$finalize()
+    expect_true(lgb.is.null.handle(bst$.__enclos_env__$private$handle))
+})
+
 context("lgb.get.eval.result")
 
 test_that("lgb.get.eval.result() should throw an informative error if booster is not an lgb.Booster", {