From 2b204d043322cd1c21fa28a4e8b92e9406504f20 Mon Sep 17 00:00:00 2001
From: David Wendt <45795991+davidwendt@users.noreply.github.com>
Date: Wed, 11 May 2022 11:39:45 -0400
Subject: [PATCH] Fix compile warning in search.cu (#10827)

Compile warning introduced with merge of PR #10802

```
10 warnings like this:
12:43:23 $SRC_DIR/cpp/src/search/search.cu(108): warning #177-D: parameter "args" was declared but never referenced
12:43:23           detected during instantiation of function "lambda [](auto &&...)->auto [with <auto-1>=<rmm::exec_policy, const
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default> &,
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default>, const
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default> &,
thrust::counting_iterator<cudf::size_type, thrust::use_default, thrust::use_default, thrust::use_default>, cudf::size_type *const &,
const cudf::row_lexicographic_comparator<cudf::nullate::DYNAMIC> &>]"
12:43:23 (121): here
```

Line 108 has a lambda refactoring that seems to confuse the compiler.
```
  auto const do_search = [find_first](auto&&... args) {
    if (find_first) {
      thrust::lower_bound(std::forward<decltype(args)>(args)...);
    } else {
      thrust::upper_bound(std::forward<decltype(args)>(args)...);
    }
  };
  do_search(rmm::exec_policy(stream),
            count_it,  count_it + haystack.num_rows(), count_it, count_it + needles.num_rows(),
            out_it, comp);
```

The warning is wrong and the compiler generates the correct code so this is likely a compiler bug.

This PR fixes the warning by replacing the lambda with an if statement.

Authors:
  - David Wendt (https://github.com/davidwendt)

Approvers:
  - Nghia Truong (https://github.com/ttnghia)
  - Yunsong Wang (https://github.com/PointKernel)

URL: https://github.com/rapidsai/cudf/pull/10827
---
 cpp/src/search/search.cu | 32 +++++++++++++++++---------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/cpp/src/search/search.cu b/cpp/src/search/search.cu
index 491ad49e020..49d0959ecc4 100644
--- a/cpp/src/search/search.cu
+++ b/cpp/src/search/search.cu
@@ -105,21 +105,23 @@ std::unique_ptr<column> search_ordered(table_view const& haystack,
                                                  column_order_dv.data(),
                                                  null_precedence_dv.data());
 
-  auto const do_search = [find_first](auto&&... args) {
-    if (find_first) {
-      thrust::lower_bound(std::forward<decltype(args)>(args)...);
-    } else {
-      thrust::upper_bound(std::forward<decltype(args)>(args)...);
-    }
-  };
-  do_search(rmm::exec_policy(stream),
-            count_it,
-            count_it + haystack.num_rows(),
-            count_it,
-            count_it + needles.num_rows(),
-            out_it,
-            comp);
-
+  if (find_first) {
+    thrust::lower_bound(rmm::exec_policy(stream),
+                        count_it,
+                        count_it + haystack.num_rows(),
+                        count_it,
+                        count_it + needles.num_rows(),
+                        out_it,
+                        comp);
+  } else {
+    thrust::upper_bound(rmm::exec_policy(stream),
+                        count_it,
+                        count_it + haystack.num_rows(),
+                        count_it,
+                        count_it + needles.num_rows(),
+                        out_it,
+                        comp);
+  }
   return result;
 }