diff --git a/tensorflow/core/BUILD b/tensorflow/core/BUILD
index 1c9bddd1dbc..b32acbedcf1 100644
--- a/tensorflow/core/BUILD
+++ b/tensorflow/core/BUILD
@@ -1974,6 +1974,7 @@ cc_library(
"//tensorflow/core/platform:abi",
"//tensorflow/core/platform:base64",
"//tensorflow/core/platform:blocking_counter",
+ "//tensorflow/core/platform:casts",
"//tensorflow/core/platform:coding",
"//tensorflow/core/platform:context",
"//tensorflow/core/platform:cord",
diff --git a/tensorflow/core/kernels/data/iterator_ops.cc b/tensorflow/core/kernels/data/iterator_ops.cc
index 2c1dceb8f4e..fbf681ac329 100644
--- a/tensorflow/core/kernels/data/iterator_ops.cc
+++ b/tensorflow/core/kernels/data/iterator_ops.cc
@@ -43,6 +43,7 @@ limitations under the License.
#include "tensorflow/core/lib/random/random.h"
#include "tensorflow/core/lib/strings/strcat.h"
#include "tensorflow/core/lib/strings/stringprintf.h"
+#include "tensorflow/core/platform/casts.h"
#include "tensorflow/core/platform/env.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/refcount.h"
diff --git a/tensorflow/core/kernels/data/iterator_ops.h b/tensorflow/core/kernels/data/iterator_ops.h
index dd80ead1f86..ad5d1517176 100644
--- a/tensorflow/core/kernels/data/iterator_ops.h
+++ b/tensorflow/core/kernels/data/iterator_ops.h
@@ -124,20 +124,6 @@ class IteratorHandleOp : public OpKernel {
// inconsistent capacities.
Status VerifyResource(IteratorResource* resource);
- template <typename To, typename From> // use like this: down_cast<T*>(foo);
- static inline To down_cast(From* f) { // so we only accept pointers
- static_assert(
- (std::is_base_of<From, typename std::remove_pointer<To>::type>::value),
- "target type not derived from source type");
-
- // We skip the assert and hence the dynamic_cast if RTTI is disabled.
-#if !defined(__GNUC__) || defined(__GXX_RTTI)
- // Uses RTTI in dbg and fastbuild. asserts are disabled in opt builds.
- assert(f == nullptr || dynamic_cast<To>(f) != nullptr);
-#endif // !defined(__GNUC__) || defined(__GXX_RTTI)
- return static_cast<To>(f);
- }
-
FunctionLibraryRuntime* CreatePrivateFLR(
OpKernelContext* ctx, std::unique_ptr<DeviceMgr>* device_mgr,
std::unique_ptr<FunctionLibraryDefinition>* flib_def,
diff --git a/tensorflow/core/kernels/functional_ops.cc b/tensorflow/core/kernels/functional_ops.cc
index d7d15d5f14b..ec749dfe9dd 100644
--- a/tensorflow/core/kernels/functional_ops.cc
+++ b/tensorflow/core/kernels/functional_ops.cc
@@ -25,6 +25,7 @@ limitations under the License.
#include "tensorflow/core/framework/tensor_shape.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/threadpool.h"
+#include "tensorflow/core/platform/casts.h"
#include "tensorflow/core/profiler/lib/traceme.h"
namespace tensorflow {
@@ -41,21 +42,6 @@ Status Instantiate(FunctionLibraryRuntime* lib, const NameAttrList& func,
return lib->Instantiate(func.name(), AttrSlice(&func.attr()), handle);
}
-template <typename To, typename From> // use like this: down_cast<T*>(foo);
-inline To down_cast(From* f) { // so we only accept pointers
- static_assert(
- (std::is_base_of<From, typename std::remove_pointer<To>::type>::value),
- "target type not derived from source type");
-
- // We skip the assert and hence the dynamic_cast if RTTI is disabled.
-#if !defined(__GNUC__) || defined(__GXX_RTTI)
- // Uses RTTI in dbg and fastbuild. asserts are disabled in opt builds.
- assert(f == nullptr || dynamic_cast<To>(f) != nullptr);
-#endif // !defined(__GNUC__) || defined(__GXX_RTTI)
-
- return static_cast<To>(f);
-}
-
// If "t" is a scalar of a supported type, returns t != 0 in "*v".
Status ToBool(gtl::ArraySlice<Tensor> t, bool* v) {
if (t.size() != 1) {
diff --git a/tensorflow/core/kernels/resource_variable_ops.cc b/tensorflow/core/kernels/resource_variable_ops.cc
index e44cfdf1ec7..80ca00388ff 100644
--- a/tensorflow/core/kernels/resource_variable_ops.cc
+++ b/tensorflow/core/kernels/resource_variable_ops.cc
@@ -73,6 +73,7 @@ limitations under the License.
#include "tensorflow/core/kernels/variable_ops.h"
#include "tensorflow/core/lib/core/errors.h"
#include "tensorflow/core/lib/core/refcount.h"
+#include "tensorflow/core/platform/casts.h"
#include "tensorflow/core/platform/mem.h"
#include "tensorflow/core/platform/mutex.h"
#include "tensorflow/core/platform/types.h"
@@ -104,7 +105,7 @@ Status CopyVariable(int output_idx, OpKernelContext* ctx, const Tensor* t) {
} else if (ctx->op_device_context() != nullptr) {
// TODO(apassos): remove the down_cast by just returning Device* from
// OpKernelContext
- Device* device = static_cast<Device*>(ctx->device());
+ Device* device = down_cast<Device*>(ctx->device());
ctx->op_device_context()->CopyTensorInSameDevice(
t, device, output, [&n, &status](const Status& s) {
status = s;
diff --git a/tensorflow/core/platform/BUILD b/tensorflow/core/platform/BUILD
index bcfb935206e..5dfeeb89c43 100644
--- a/tensorflow/core/platform/BUILD
+++ b/tensorflow/core/platform/BUILD
@@ -158,6 +158,14 @@ cc_library(
],
)
+cc_library(
+ name = "casts",
+ hdrs = ["casts.h"],
+ deps = [
+ ":platform",
+ ] + tf_platform_deps("casts"),
+)
+
cc_library(
name = "cuda",
hdrs = ["cuda.h"],
@@ -1060,6 +1068,7 @@ filegroup(
name = "lib_hdrs",
srcs = [
"abi.h",
+ "casts.h",
"context.h",
"cpu_feature_guard.h",
"cpu_info.h",
@@ -1254,6 +1263,7 @@ filegroup(
"//tensorflow/core/platform:base64.h",
"//tensorflow/core/platform:blocking_counter.h",
"//tensorflow/core/platform:byte_order.h",
+ "//tensorflow/core/platform:casts.h",
"//tensorflow/core/platform:coding.cc",
"//tensorflow/core/platform:coding.h",
"//tensorflow/core/platform:context.h",
@@ -1360,6 +1370,7 @@ filegroup(
name = "legacy_srcs_no_runtime",
srcs = [
":legacy_srcs_common",
+ "//tensorflow/core/platform/default:casts.h",
"//tensorflow/core/platform/default:context.h",
"//tensorflow/core/platform/default:cord.h",
"//tensorflow/core/platform/default:dynamic_annotations.h",
diff --git a/tensorflow/core/platform/casts.h b/tensorflow/core/platform/casts.h
new file mode 100644
index 00000000000..be7be00bd45
--- /dev/null
+++ b/tensorflow/core/platform/casts.h
@@ -0,0 +1,31 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_CORE_PLATFORM_CASTS_H_
+#define TENSORFLOW_CORE_PLATFORM_CASTS_H_
+
+#include "tensorflow/core/platform/platform.h"
+
+#if defined(PLATFORM_GOOGLE)
+#include "tensorflow/core/platform/google/casts.h"
+#elif defined(PLATFORM_POSIX) || defined(PLATFORM_POSIX_ANDROID) || \
+ defined(PLATFORM_GOOGLE_ANDROID) || defined(PLATFORM_POSIX_IOS) || \
+ defined(PLATFORM_GOOGLE_IOS) || defined(PLATFORM_WINDOWS)
+#include "tensorflow/core/platform/default/casts.h"
+#else
+#error Define the appropriate PLATFORM_<foo> macro for this platform
+#endif
+
+#endif // TENSORFLOW_CORE_PLATFORM_CASTS_H_
diff --git a/tensorflow/core/platform/default/BUILD b/tensorflow/core/platform/default/BUILD
index 491f84536cf..346018153d5 100644
--- a/tensorflow/core/platform/default/BUILD
+++ b/tensorflow/core/platform/default/BUILD
@@ -9,6 +9,16 @@ package(
licenses = ["notice"], # Apache 2.0
)
+cc_library(
+ name = "casts",
+ hdrs = ["casts.h"],
+ tags = [
+ "manual",
+ "no_oss",
+ "nobuilder",
+ ],
+)
+
cc_library(
name = "context",
hdrs = ["//tensorflow/core/platform:context.h"],
diff --git a/tensorflow/core/platform/default/build_config.bzl b/tensorflow/core/platform/default/build_config.bzl
index 61fe01cb262..3c0a4676eff 100644
--- a/tensorflow/core/platform/default/build_config.bzl
+++ b/tensorflow/core/platform/default/build_config.bzl
@@ -541,6 +541,7 @@ def tf_proto_library(
def tf_additional_lib_hdrs():
return [
+ "//tensorflow/core/platform/default:casts.h",
"//tensorflow/core/platform/default:context.h",
"//tensorflow/core/platform/default:cord.h",
"//tensorflow/core/platform/default:dynamic_annotations.h",
diff --git a/tensorflow/core/platform/default/casts.h b/tensorflow/core/platform/default/casts.h
new file mode 100644
index 00000000000..ed1d2a66812
--- /dev/null
+++ b/tensorflow/core/platform/default/casts.h
@@ -0,0 +1,92 @@
+/* Copyright 2020 The TensorFlow Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+==============================================================================*/
+
+#ifndef TENSORFLOW_CORE_PLATFORM_DEFAULT_CASTS_H_
+#define TENSORFLOW_CORE_PLATFORM_DEFAULT_CASTS_H_
+
+#include <assert.h> // for use with down_cast<>
+
+#include <type_traits>
+
+namespace tensorflow {
+
+// An "upcast", i.e. a conversion from a pointer to an object to a pointer to a
+// base subobject, always succeeds if the base is unambiguous and accessible,
+// and so it's fine to use implicit_cast.
+//
+// A "downcast", i.e. a conversion from a pointer to an object to a pointer
+// to a more-derived object that may contain the original object as a base
+// subobject, cannot safely be done using static_cast, because you do not
+// generally know whether the source object is really the base subobject of
+// a containing, more-derived object of the target type. Thus, when you
+// downcast in a polymorphic type hierarchy, you should use the following
+// function template.
+//
+// In debug mode, we use dynamic_cast to double-check whether the downcast is
+// legal (we die if it's not). In normal mode, we do the efficient static_cast
+// instead. Thus, it's important to test in debug mode to make sure the cast is
+// legal!
+//
+// This is the only place in the codebase we should use dynamic_cast.
+// In particular, you should NOT use dynamic_cast for RTTI, e.g. for
+// code like this:
+// if (auto* p = dynamic_cast<Subclass1*>(foo)) HandleASubclass1Object(p);
+// if (auto* p = dynamic_cast<Subclass2*>(foo)) HandleASubclass2Object(p);
+// You should design the code some other way not to need this.
+
+template <typename To, typename From> // use like this: down_cast<T*>(foo);
+inline To down_cast(From* f) { // so we only accept pointers
+ static_assert(
+ (std::is_base_of<From, typename std::remove_pointer<To>::type>::value),
+ "target type not derived from source type");
+
+ // We skip the assert and hence the dynamic_cast if RTTI is disabled.
+#if !defined(__GNUC__) || defined(__GXX_RTTI)
+ // Uses RTTI in dbg and fastbuild. asserts are disabled in opt builds.
+ assert(f == nullptr || dynamic_cast<To>(f) != nullptr);
+#endif // !defined(__GNUC__) || defined(__GXX_RTTI)
+
+ return static_cast<To>(f);
+}
+
+// Overload of down_cast for references. Use like this: down_cast<T&>(foo).
+// The code is slightly convoluted because we're still using the pointer
+// form of dynamic cast. (The reference form throws an exception if it
+// fails.)
+//
+// There's no need for a special const overload either for the pointer
+// or the reference form. If you call down_cast with a const T&, the
+// compiler will just bind From to const T.
+template <typename To, typename From>
+inline To down_cast(From& f) {
+ static_assert(std::is_lvalue_reference<To>::value,
+ "target type not a reference");
+ static_assert(
+ (std::is_base_of<From, typename std::remove_reference<To>::type>::value),
+ "target type not derived from source type");
+
+ // We skip the assert and hence the dynamic_cast if RTTI is disabled.
+#if !defined(__GNUC__) || defined(__GXX_RTTI)
+ // RTTI: debug mode only
+ assert(dynamic_cast<typename std::remove_reference<To>::type*>(&f) !=
+ nullptr);
+#endif // !defined(__GNUC__) || defined(__GXX_RTTI)
+
+ return static_cast<To>(f);
+}
+
+} // namespace tensorflow
+
+#endif // TENSORFLOW_CORE_PLATFORM_DEFAULT_CASTS_H_