From 87d316ddb7826803240e306db24a4c781c380581 Mon Sep 17 00:00:00 2001
From: Attila Krasznahorkay <Attila.Krasznahorkay@cern.ch>
Date: Mon, 8 Nov 2021 14:54:43 +0100
Subject: [PATCH] Made VecMem export its "language files" during installation.

Making it possible to make use of VecMem's SYCL and HIP build
infrastructure after "finding" an installed version of VecMem.

Introduced "component flags" for the CUDA, HIP and SYCL libraries,
so that find_package(...) calls could explicitly ask for some of
the optional libraries to be available.
---
 cmake/vecmem-check-language.cmake | 16 ++++++-----
 cmake/vecmem-config.cmake.in      | 45 ++++++++++++++++++++++++++++---
 cmake/vecmem-packaging.cmake      | 10 +++++++
 3 files changed, 61 insertions(+), 10 deletions(-)

diff --git a/cmake/vecmem-check-language.cmake b/cmake/vecmem-check-language.cmake
index 084f5272..4830c8d8 100644
--- a/cmake/vecmem-check-language.cmake
+++ b/cmake/vecmem-check-language.cmake
@@ -4,16 +4,18 @@
 #
 # Mozilla Public License Version 2.0
 
-# Make sure that the code is not included more than once.
-include_guard( GLOBAL )
-
 # CMake include(s).
 include( CheckLanguage )
 
+# Cache the location of this directory.
+set( VECMEM_LANGUAGE_DIR "${CMAKE_CURRENT_LIST_DIR}" CACHE PATH
+   "Directory holding the VecMem language files" )
+mark_as_advanced( VECMEM_LANGUAGE_DIR )
+
 # Teach CMake about VecMem's custom language files.
 list( INSERT CMAKE_MODULE_PATH 0
-   "${CMAKE_CURRENT_LIST_DIR}/hip"
-   "${CMAKE_CURRENT_LIST_DIR}/sycl" )
+   "${VECMEM_LANGUAGE_DIR}/hip"
+   "${VECMEM_LANGUAGE_DIR}/sycl" )
 
 # Code mimicking CMake's CheckLanguage.cmake module. But making sure that the
 # VecMem specific code is used while looking for the non-standard languages.
@@ -46,8 +48,8 @@ macro( vecmem_check_language lang )
             "cmake_minimum_required( VERSION ${CMAKE_VERSION} )\n"
             "project( Check${lang} LANGUAGES CXX )\n"
             "list( INSERT CMAKE_MODULE_PATH 0 "
-            "      \"${CMAKE_CURRENT_LIST_DIR}/hip\" "
-            "      \"${CMAKE_CURRENT_LIST_DIR}/sycl\" )\n"
+            "      \"${VECMEM_LANGUAGE_DIR}/hip\" "
+            "      \"${VECMEM_LANGUAGE_DIR}/sycl\" )\n"
             "enable_language( ${lang} )\n"
             "file( WRITE \"\${CMAKE_CURRENT_BINARY_DIR}/result.cmake\"\n"
             "   \"set( CMAKE_${lang}_COMPILER \\\"\${CMAKE_${lang}_COMPILER}\\\" )\" )" )
diff --git a/cmake/vecmem-config.cmake.in b/cmake/vecmem-config.cmake.in
index 929bd271..b5c73709 100644
--- a/cmake/vecmem-config.cmake.in
+++ b/cmake/vecmem-config.cmake.in
@@ -13,11 +13,50 @@ set_and_check( vecmem_INCLUDE_DIR "@PACKAGE_CMAKE_INSTALL_INCLUDEDIR@" )
 set_and_check( vecmem_LIBRARY_DIR "@PACKAGE_CMAKE_INSTALL_LIBDIR@" )
 set_and_check( vecmem_CMAKE_DIR "@PACKAGE_CMAKE_INSTALL_CMAKEDIR@" )
 
+# Include the file listing all the imported targets and options.
+include( "${vecmem_CMAKE_DIR}/vecmem-config-targets.cmake" )
+
+# Set up additional variables, based on the imported targets. These are mostly
+# just here for handling COMPONENT arguments for find_package(...).
+set( vecmem_CORE_LIBRARY vecmem::core )
+if( TARGET vecmem::cuda )
+   set( vecmem_CUDA_LIBRARY vecmem::cuda )
+else()
+   set( vecmem_CUDA_LIBRARY vecmem::cuda-NOTFOUND )
+endif()
+if( TARGET vecmem::hip )
+   set( vecmem_HIP_LIBRARY vecmem::hip )
+else()
+   set( vecmem_HIP_LIBRARY vecmem::hip-NOTFOUND )
+endif()
+if( TARGET vecmem::sycl )
+   set( vecmem_SYCL_LIBRARY vecmem::sycl )
+else()
+   set( vecmem_SYCL_LIBRARY vecmem::sycl-NOTFOUND )
+endif()
+
+# If the user asked for the CUDA/HIP/SYCL components explicitly, make
+# sure that they would exist in the installation.
+set( vecmem_REQUIRED_LIBS vecmem_CORE_LIBRARY )
+foreach( comp "CUDA" "HIP" "SYCL" )
+   if( "${vecmem_FIND_COMPONENTS}" MATCHES "${comp}" )
+      list( APPEND vecmem_REQUIRED_LIBS vecmem_${comp}_LIBRARY )
+   endif()
+endforeach()
+
 # Print a standard information message about the package being found.
 include( FindPackageHandleStandardArgs )
 find_package_handle_standard_args( vecmem REQUIRED_VARS
-   CMAKE_CURRENT_LIST_FILE
+   CMAKE_CURRENT_LIST_FILE ${vecmem_REQUIRED_LIBS}
    VERSION_VAR vecmem_VERSION )
 
-# Include the file listing all the imported targets and options.
-include( "${vecmem_CMAKE_DIR}/vecmem-config-targets.cmake" )
+# Clean up.
+unset( vecmem_REQUIRED_LIBS )
+
+# Set up the "language helper code" coming with the installation, if the
+# user asks for it.
+set_and_check( vecmem_LANGUAGE_FILE
+   "${vecmem_CMAKE_DIR}/vecmem-check-language.cmake" )
+if( "${vecmem_FIND_COMPONENTS}" MATCHES "LANGUAGE" )
+   include( "${vecmem_LANGUAGE_FILE}" )
+endif()
diff --git a/cmake/vecmem-packaging.cmake b/cmake/vecmem-packaging.cmake
index be680d74..cdf3afe2 100644
--- a/cmake/vecmem-packaging.cmake
+++ b/cmake/vecmem-packaging.cmake
@@ -29,3 +29,13 @@ install( FILES
    "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/vecmem-config.cmake"
    "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/vecmem-config-version.cmake"
    DESTINATION "${CMAKE_INSTALL_CMAKEDIR}" )
+
+# Install the "language helper" files.
+install( FILES "${CMAKE_CURRENT_SOURCE_DIR}/cmake/vecmem-check-language.cmake"
+   DESTINATION "${CMAKE_INSTALL_CMAKEDIR}" )
+install( DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}/cmake/hip"
+                   "${CMAKE_CURRENT_SOURCE_DIR}/cmake/sycl"
+   DESTINATION "${CMAKE_INSTALL_CMAKEDIR}" )
+
+# Clean up.
+unset( CMAKE_INSTALL_CMAKEDIR )