From b49ff6151e4dc080cd9fe8200fd2672e9bbba51c Mon Sep 17 00:00:00 2001
From: Scott McKay <skottmckay@gmail.com>
Date: Fri, 25 Sep 2020 06:50:14 +1000
Subject: [PATCH] Workaround issue with VS2017 compiler. (#5279)

The definitions for some Eigen classes don't get pulled in leading to errors. Split out the broadcast function creation logic from the functions using std::enable_if to workaround that.
---
 .../core/providers/cpu/tensor/where_op.cc     | 23 +++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/onnxruntime/core/providers/cpu/tensor/where_op.cc b/onnxruntime/core/providers/cpu/tensor/where_op.cc
index 5b4f1b9159..05be3d4ff4 100644
--- a/onnxruntime/core/providers/cpu/tensor/where_op.cc
+++ b/onnxruntime/core/providers/cpu/tensor/where_op.cc
@@ -49,7 +49,7 @@ template <typename T, typename R>
 using EnableIfEigenNotScalar = typename std::enable_if<!std::is_arithmetic<T>::value, R>::type;
 
 template <typename T>
-EnableIfEigenScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
+ProcessBroadcastSpanFuncs CreateScalarBroadcastFuncs() {
   return ProcessBroadcastSpanFuncs{
       [](BroadcastHelper& per_iter_bh) {
         bool target = per_iter_bh.GetUserData();
@@ -81,7 +81,7 @@ EnableIfEigenScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
 }
 
 template <typename T>
-EnableIfEigenNotScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
+ProcessBroadcastSpanFuncs CreateNonScalarBroadcastFuncs() {
   return ProcessBroadcastSpanFuncs{
       [](BroadcastHelper& per_iter_bh) {
         bool target = per_iter_bh.GetUserData();
@@ -116,6 +116,19 @@ EnableIfEigenNotScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
       }};
 }
 
+template <typename T>
+EnableIfEigenScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
+  // NOTE: Workaround a VS2017 bug by calling a separate function to create the broadcast funcs.
+  // If we create them directly here it doesn't bring in the definitions of the Eigen classes leading to
+  // a 'class has no constructors' error
+  return CreateScalarBroadcastFuncs<T>();
+}
+
+template <typename T>
+EnableIfEigenNotScalar<T, ProcessBroadcastSpanFuncs> SelectBroadcastFuncs() {
+  return CreateNonScalarBroadcastFuncs<T>();
+}
+
 template <typename T>
 void MergeScalarAndVector(EigenVectorMap<T> output, const T& scalar_value, ConstEigenVectorMap<T> vector_value) {
   if (scalar_value != T{}) {
@@ -231,8 +244,13 @@ Status Where<T>::Compute(OpKernelContext* context) const {
   //   X_selection = condition ? X : default value
   // Similarly, we broadcast over condition and Y to select the values from Y:
   //   Y_selection = !condition ? Y : default value
+  //
+  // These selections are handled within UntypedSelect.
+  //
   // Finally, we broadcast over and merge X_selection and Y_selection:
   //   output = (X_selection != default value) ? X_selection : Y_selection
+  //
+  // The merging is handled within UntypedMerge.
   auto X_selection_tensor = UntypedSelect(*context, true, tensor_allocator, typed_tensor_allocation, funcs);
   auto Y_selection_tensor = UntypedSelect(*context, false, tensor_allocator, typed_tensor_allocation, funcs);
 
@@ -240,4 +258,5 @@ Status Where<T>::Compute(OpKernelContext* context) const {
 
   return Status::OK();
 }
+
 }  // namespace onnxruntime