[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, 12 insertions, 1 deletions

diff --git a/tensorflow/c/c_api.cc b/tensorflow/c/c_api.cc
index 09a03639d6..37c8302e08 100644
--- a/tensorflow/c/c_api.cc
+++ b/tensorflow/c/c_api.cc
@@ -2414,7 +2414,18 @@ void TF_AddGradients(TF_Graph* g, TF_Output* y, int ny, TF_Output* x, int nx,
     for (int i = first_new_node_id; i < g->graph.num_node_ids(); ++i) {
       Node* n = g->graph.FindNodeId(i);
       if (n == nullptr) continue;
-      g->name_map[n->name()] = n;
+      // We have a convoluted scheme here: Using the C++ graph construction API
+      // to add potentially many nodes to the graph without running the checks
+      // (such as uniqueness of the names of nodes) we run with other functions
+      // that add a node to the graph (like TF_FinishOperation).
+      if (!g->name_map.insert(std::make_pair(n->name(), n)).second) {
+        status->status = tensorflow::errors::Internal(
+            "BUG: The API allowed construction of a graph with duplicate node "
+            "names (",
+            n->name(),
+            "). This is a bug. Please file an issue at "
+            "https://github.com/tensorflow/tensorflow/issues.");
+      }
     }
   }