From 833caddb863a56c4039a715d7988f09b2f9ace1a Mon Sep 17 00:00:00 2001
From: Nghia Truong <nghiatruong.vn@gmail.com>
Date: Wed, 13 Jul 2022 13:19:19 -0700
Subject: [PATCH] Fix compile error due to missing header (#11257)
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The recently merged PR (https://github.com/rapidsai/cudf/pull/11137) did not include the `<optional>` header which may cause compile error in some systems (in particular, CUDA 11.7 + gcc-11.2):
```
error: ‘std::optional’ has not been declared
error: ‘optional’ in namespace ‘std’ does not name a template type
```

This PR adds that missing header to fix the compile issue.

Authors:
  - Nghia Truong (https://github.com/ttnghia)

Approvers:
  - Gera Shegalov (https://github.com/gerashegalov)
  - David Wendt (https://github.com/davidwendt)
  - Mike Wilson (https://github.com/hyperbolic2346)

URL: https://github.com/rapidsai/cudf/pull/11257
---
 cpp/include/cudf/detail/null_mask.cuh           | 1 +
 cpp/include/cudf/detail/reduction_functions.hpp | 2 ++
 cpp/include/cudf/reduction.hpp                  | 2 ++
 cpp/src/reductions/simple_segmented.cuh         | 1 +
 4 files changed, 6 insertions(+)

diff --git a/cpp/include/cudf/detail/null_mask.cuh b/cpp/include/cudf/detail/null_mask.cuh
index 8b6edd77476..c596404b784 100644
--- a/cpp/include/cudf/detail/null_mask.cuh
+++ b/cpp/include/cudf/detail/null_mask.cuh
@@ -39,6 +39,7 @@
 
 #include <algorithm>
 #include <iterator>
+#include <optional>
 #include <vector>
 
 namespace cudf {
diff --git a/cpp/include/cudf/detail/reduction_functions.hpp b/cpp/include/cudf/detail/reduction_functions.hpp
index 58cf2dc84e7..7877fe13951 100644
--- a/cpp/include/cudf/detail/reduction_functions.hpp
+++ b/cpp/include/cudf/detail/reduction_functions.hpp
@@ -23,6 +23,8 @@
 
 #include <rmm/cuda_stream_view.hpp>
 
+#include <optional>
+
 namespace cudf {
 namespace reduction {
 /**
diff --git a/cpp/include/cudf/reduction.hpp b/cpp/include/cudf/reduction.hpp
index e479c6f47ce..083892aa856 100644
--- a/cpp/include/cudf/reduction.hpp
+++ b/cpp/include/cudf/reduction.hpp
@@ -21,6 +21,8 @@
 
 #include <rmm/mr/device/per_device_resource.hpp>
 
+#include <optional>
+
 namespace cudf {
 /**
  * @addtogroup aggregation_reduction
diff --git a/cpp/src/reductions/simple_segmented.cuh b/cpp/src/reductions/simple_segmented.cuh
index 7dde713e638..774b9075736 100644
--- a/cpp/src/reductions/simple_segmented.cuh
+++ b/cpp/src/reductions/simple_segmented.cuh
@@ -38,6 +38,7 @@
 #include <thrust/iterator/transform_iterator.h>
 #include <thrust/iterator/zip_iterator.h>
 
+#include <optional>
 #include <type_traits>
 
 namespace cudf {