[C API]: Bugfix for TF_AddGradients.

TF_AddGradients could create nodes in the graph with names that conflicted with
other nodes in the graph. This would most clearly happen if TF_AddGradients()
was called twice on the same graph, and could also happen if there were other
nodes in the graph that happened to have "gradients" as a prefix of their name.

Fix that.

The added test in c_api_test.cc would fail in the call to TF_SessionRun() with
  Node 'gradients/OnesLike' is not unique
without the changes to c_api.cc and c_api_internal.h

While at it, also fixed a possible name collision bug when using the C++ API
to constructor graphs (using Scope).

Thanks @karllessard for pointing this out.

PiperOrigin-RevId: 202087996

1 files changed, 60 insertions, 5 deletions

diff --git a/tensorflow/c/c_api_test.cc b/tensorflow/c/c_api_test.cc
index 577f10c5e6..bc04b53fbb 100644
--- a/tensorflow/c/c_api_test.cc
+++ b/tensorflow/c/c_api_test.cc
@@ -1160,7 +1160,7 @@ TEST(CAPI, GetOpDef) {
 }
 
 void StringVectorToArrays(const std::vector<string>& v,
-                          std::unique_ptr<const void* []>* ptrs,
+                          std::unique_ptr<const void*[]>* ptrs,
                           std::unique_ptr<size_t[]>* lens) {
   ptrs->reset(new const void*[v.size()]);
   lens->reset(new size_t[v.size()]);
@@ -1196,7 +1196,7 @@ class CApiColocationTest : public ::testing::Test {
 
   void SetViaStringList(TF_OperationDescription* desc,
                         const std::vector<string>& list) {
-    std::unique_ptr<const void* []> list_ptrs;
+    std::unique_ptr<const void*[]> list_ptrs;
     std::unique_ptr<size_t[]> list_lens;
     StringVectorToArrays(list, &list_ptrs, &list_lens);
     TF_SetAttrStringList(desc, tensorflow::kColocationAttrName, list_ptrs.get(),
@@ -1700,6 +1700,61 @@ TEST_F(CApiGradientsTest, OpWithNoGradientRegistered_NoGradInputs) {
   TestGradientsError(false);
 }
 
+void ScalarFloatFromTensor(const TF_Tensor* t, float* f) {
+  ASSERT_TRUE(t != nullptr);
+  ASSERT_EQ(TF_FLOAT, TF_TensorType(t));
+  ASSERT_EQ(0, TF_NumDims(t));
+  ASSERT_EQ(4, TF_TensorByteSize(t));
+  float* p = static_cast<float*>(TF_TensorData(t));
+  *f = *p;
+}
+
+TEST_F(CApiGradientsTest, MultipleCallsToAddGradients) {
+  const float X = 3.0f, Y = 7.0f;
+  TF_Operation* x = Placeholder(graph_, s_, "x", TF_FLOAT);
+  TF_Operation* y = Placeholder(graph_, s_, "y", TF_FLOAT);
+  TF_Operation* xy = Mul(x, y, graph_, s_, "xy");
+  TF_Output dxy_dx, dxy_dy;
+
+  TF_Output outputs[1] = {{xy, 0}};
+  TF_Output inputs[1] = {{x, 0}};
+  TF_AddGradients(graph_, outputs, 1, inputs, 1, nullptr, s_, &dxy_dx);
+  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
+
+  inputs[0] = {y, 0};
+  TF_AddGradients(graph_, outputs, 1, inputs, 1, nullptr, s_, &dxy_dy);
+  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
+
+  TF_SessionOptions* opts = TF_NewSessionOptions();
+  TF_Session* sess = TF_NewSession(graph_, opts, s_);
+  TF_DeleteSessionOptions(opts);
+  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
+
+  TF_Output feeds[] = {{x, 0}, {y, 0}};
+  TF_Tensor* feedValues[] = {FloatTensor(X), FloatTensor(Y)};
+  TF_Output fetches[] = {dxy_dx, dxy_dy};
+  TF_Tensor* fetchValues[] = {nullptr, nullptr};
+
+  TF_SessionRun(sess, nullptr /* run_options */, feeds, feedValues, 2, fetches,
+                fetchValues, 2, nullptr /* target_opers */, 0,
+                nullptr /* run_metadata */, s_);
+  TF_DeleteTensor(feedValues[0]);
+  TF_DeleteTensor(feedValues[1]);
+  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
+  TF_DeleteSession(sess, s_);
+  ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
+
+  float dxy_dxValue = 0.0f, dxy_dyValue = 0.0f;
+  ScalarFloatFromTensor(fetchValues[0], &dxy_dxValue);
+  EXPECT_EQ(Y, dxy_dxValue);
+
+  ScalarFloatFromTensor(fetchValues[1], &dxy_dyValue);
+  EXPECT_EQ(X, dxy_dyValue);
+
+  TF_DeleteTensor(fetchValues[0]);
+  TF_DeleteTensor(fetchValues[1]);
+}
+
 // REGISTER_OP for CApiAttributesTest test cases.
 // Registers two ops, each with a single attribute called 'v'.
 // The attribute in one op will have a type 'type', the other
@@ -1784,7 +1839,7 @@ TEST_F(CApiAttributesTest, String) {
 
 TEST_F(CApiAttributesTest, StringList) {
   std::vector<string> list = {"bugs", "bunny", "duck"};
-  std::unique_ptr<const void* []> list_ptrs;
+  std::unique_ptr<const void*[]> list_ptrs;
   std::unique_ptr<size_t[]> list_lens;
   StringVectorToArrays(list, &list_ptrs, &list_lens);
   int list_total_size = 0;
@@ -1800,7 +1855,7 @@ TEST_F(CApiAttributesTest, StringList) {
   ASSERT_EQ(TF_OK, TF_GetCode(s_)) << TF_Message(s_);
 
   EXPECT_TF_META("v", list.size(), TF_ATTR_STRING, list_total_size);
-  std::unique_ptr<void* []> values(new void*[list.size()]);
+  std::unique_ptr<void*[]> values(new void*[list.size()]);
   std::unique_ptr<size_t[]> lens(new size_t[list.size()]);
   std::unique_ptr<char[]> storage(new char[list_total_size]);
   TF_OperationGetAttrStringList(oper, "v", values.get(), lens.get(),
@@ -2025,7 +2080,7 @@ TEST_F(CApiAttributesTest, TensorShapeProtoList) {
   tensorflow::PartialTensorShape(pts2).AsProto(&proto);
   proto.SerializeToString(&bytes2);
 
-  std::unique_ptr<const void* []> list_ptrs;
+  std::unique_ptr<const void*[]> list_ptrs;
   std::unique_ptr<size_t[]> list_lens;
   const std::vector<string> list = {bytes1, bytes2};
   StringVectorToArrays(list, &list_ptrs, &list_lens);