From a39e385cc6be20754f859dd266021ab1d88459d3 Mon Sep 17 00:00:00 2001
From: Allison Vacanti <alliepiper16@gmail.com>
Date: Tue, 22 Sep 2020 16:53:51 -0400
Subject: [PATCH] Add support for importing CUB targets with add_subdirectory.

---
 CMakeLists.txt                           |  8 ++++++
 cmake/CubAddSubdir.cmake                 |  4 +++
 examples/CMakeLists.txt                  |  1 +
 examples/cmake/CMakeLists.txt            | 11 ++++++++
 examples/cmake/add_subdir/CMakeLists.txt | 32 ++++++++++++++++++++++++
 examples/cmake/add_subdir/dummy.cu       |  8 ++++++
 6 files changed, 64 insertions(+)
 create mode 100644 cmake/CubAddSubdir.cmake
 create mode 100644 examples/cmake/CMakeLists.txt
 create mode 100644 examples/cmake/add_subdir/CMakeLists.txt
 create mode 100644 examples/cmake/add_subdir/dummy.cu

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bb6f345c8e..410efba90f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,3 +1,11 @@
+# Support adding CUB to a parent project via add_subdirectory.
+# See examples/cmake/add_subdir/CMakeLists.txt for details.
+if (NOT "${CMAKE_SOURCE_DIR}" STREQUAL "${CMAKE_CURRENT_LIST_DIR}" AND
+    NOT CUB_IN_THRUST)
+  include(cmake/CubAddSubdir.cmake)
+  return()
+endif()
+
 # Will be increased to 3.18 when C++17 is enabled:
 cmake_minimum_required(VERSION 3.15)
 
diff --git a/cmake/CubAddSubdir.cmake b/cmake/CubAddSubdir.cmake
new file mode 100644
index 0000000000..99829b196c
--- /dev/null
+++ b/cmake/CubAddSubdir.cmake
@@ -0,0 +1,4 @@
+find_package(CUB REQUIRED CONFIG
+  NO_DEFAULT_PATH # Only check the explicit path in HINTS:
+  HINTS "${CMAKE_CURRENT_LIST_DIR}/.."
+)
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index eabb7d5009..9d93253e84 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -54,5 +54,6 @@ function(cub_add_example target_name_var example_name example_src cub_target)
   )
 endfunction()
 
+add_subdirectory(cmake)
 add_subdirectory(block)
 add_subdirectory(device)
diff --git a/examples/cmake/CMakeLists.txt b/examples/cmake/CMakeLists.txt
new file mode 100644
index 0000000000..0fc9296f5d
--- /dev/null
+++ b/examples/cmake/CMakeLists.txt
@@ -0,0 +1,11 @@
+add_test(
+  NAME cub.example.cmake.add_subdir
+  COMMAND "${CMAKE_COMMAND}"
+    --log-level=VERBOSE
+    -G "${CMAKE_GENERATOR}"
+    -S "${CMAKE_CURRENT_SOURCE_DIR}/add_subdir"
+    -B "${CMAKE_CURRENT_BINARY_DIR}/add_subdir"
+    -D "CUB_ROOT=${CUB_SOURCE_DIR}"
+    -D "CMAKE_CUDA_COMPILER=${CMAKE_CUDA_COMPILER}"
+    -D "CMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}"
+)
diff --git a/examples/cmake/add_subdir/CMakeLists.txt b/examples/cmake/add_subdir/CMakeLists.txt
new file mode 100644
index 0000000000..41a460593d
--- /dev/null
+++ b/examples/cmake/add_subdir/CMakeLists.txt
@@ -0,0 +1,32 @@
+# This example demonstrates / tests adding CUB via a CMake add_subdirectory
+# call from a parent project.
+
+cmake_minimum_required(VERSION 3.15)
+
+# Silence warnings about empty CUDA_ARCHITECTURES properties on example targets:
+if (CMAKE_VERSION VERSION_GREATER_EQUAL 3.18)
+  cmake_policy(SET CMP0104 OLD)
+endif()
+
+project(CubAddSubDirExample CUDA)
+
+# Use your project's checkout of CUB here, for most cases
+# `add_subdirectory(cub)` will be sufficient.
+add_subdirectory("${CUB_ROOT}" cub)
+
+# Link the CUB::CUB target to your project's targets
+add_executable(HelloCUB dummy.cu)
+target_link_libraries(HelloCUB CUB::CUB)
+
+#
+# Validation
+#
+
+function(assert_target target_name)
+  if (NOT TARGET "${target_name}")
+    message(FATAL_ERROR "Target '${target_name}' not defined.")
+  endif()
+endfunction()
+
+assert_target(CUB::CUB)
+assert_target(HelloCUB)
diff --git a/examples/cmake/add_subdir/dummy.cu b/examples/cmake/add_subdir/dummy.cu
new file mode 100644
index 0000000000..d3d1870833
--- /dev/null
+++ b/examples/cmake/add_subdir/dummy.cu
@@ -0,0 +1,8 @@
+#include <cub/config.cuh>
+
+#include <iostream>
+
+int main()
+{
+  std::cout << "Hello from CUB version " << CUB_VERSION << ":\n";
+}