Require a C++ compiler only when needed

Co-authored-by: [email protected]

Author: PatKamin

.github/workflows/pr_push.yml

@@ -11,15 +11,16 @@ jobs:
         name: Fast build
         strategy:
             matrix:
-                os: [ubuntu-latest, windows-latest]
+                os: [ubuntu-latest]
+                nproc: ['$(nproc)']
+                pool_scalable: ['ON']
+                disjoint: ['ON', 'OFF']
+                jemalloc: ['ON']
                 include:
-                    - os: ubuntu-latest
-                      nproc: $(nproc)
-                      pool_scalable: 'ON'
-                      jemalloc: 'ON'
                     - os: windows-latest
                       nproc: $Env:NUMBER_OF_PROCESSORS
                       pool_scalable: 'OFF'
+                      disjoint: 'OFF'
                       jemalloc: 'OFF'
         runs-on: ${{matrix.os}}
 
@@ -42,8 +43,9 @@ jobs:
             -DUMF_DEVELOPER_MODE=ON
             -DUMF_ENABLE_POOL_TRACKING=ON
             -DUMF_BUILD_LIBUMF_POOL_SCALABLE=${{matrix.pool_scalable}}
-            -DUMF_BUILD_LIBUMF_POOL_DISJOINT=ON
+            -DUMF_BUILD_LIBUMF_POOL_DISJOINT=${{matrix.disjoint}}
             -DUMF_BUILD_LIBUMF_POOL_JEMALLOC=${{matrix.jemalloc}}
+            -DUMF_BUILD_TESTS=OFF
 
         - name: Build
           run: >

CMakeLists.txt

@@ -3,17 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 cmake_minimum_required(VERSION 3.14.0 FATAL_ERROR)
-project(unified-memory-framework VERSION 0.1.0)
-
-set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_CXX_STANDARD_REQUIRED YES)
-
-include(CTest)
-include(CMakePackageConfigHelpers)
-include(GNUInstallDirs)
-
-list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
-include(helpers)
+project(unified-memory-framework VERSION 0.1.0 LANGUAGES C)
 
 # Build Options
 option(UMF_BUILD_SHARED_LIBRARY "Build UMF as shared library" OFF)
@@ -31,6 +21,28 @@ option(USE_UBSAN "Enable UndefinedBehaviorSanitizer checks" OFF)
 option(USE_TSAN "Enable ThreadSanitizer checks" OFF)
 option(USE_MSAN "Enable MemorySanitizer checks" OFF)
 
+# For using the options listed in the OPTIONS_REQUIRING_CXX variable
+# a C++17 compiler is required. Moreover, if these options are not set,
+# CMake will set up a strict C build, without C++ support.
+set(OPTIONS_REQUIRING_CXX
+    "UMF_BUILD_TESTS"
+    "UMF_BUILD_LIBUMF_POOL_DISJOINT")
+foreach(option_name ${OPTIONS_REQUIRING_CXX})
+    if(${option_name})
+        enable_language(CXX)
+        set(CMAKE_CXX_STANDARD 17)
+        set(CMAKE_CXX_STANDARD_REQUIRED YES)
+        break()
+    endif()
+endforeach()
+
+include(CTest)
+include(CMakePackageConfigHelpers)
+include(GNUInstallDirs)
+
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+include(helpers)
+
 if(${CMAKE_SYSTEM_NAME} MATCHES "Linux")
     set(LINUX TRUE)
     set(OS_NAME "linux")

cmake/helpers.cmake

@@ -135,16 +135,19 @@ macro(add_sanitizer_flag flag)
 
     # Check C and CXX compilers for given sanitizer flag.
     check_c_compiler_flag("${SANITIZER_FLAG}" "C_${check_name}")
-    check_cxx_compiler_flag("${SANITIZER_FLAG}" "CXX_${check_name}")
+    if (CMAKE_CXX_COMPILE_FEATURES)
+        check_cxx_compiler_flag("${SANITIZER_FLAG}" "CXX_${check_name}")
+    endif()
     if (NOT ${C_${check_name}} OR NOT ${CXX_${check_name}})
         message(FATAL_ERROR "${flag} sanitizer is not supported (either by C or CXX compiler)")
     endif()
 
     # Check C and CXX compilers for sanitizer arguments.
     if (${SANITIZER_ARGS})
         check_c_compiler_flag("${SANITIZER_ARGS}" "C_HAS_SAN_ARGS")
-        check_cxx_compiler_flag("${SANITIZER_ARGS}" "CXX_HAS_SAN_ARGS")
-
+        if (CMAKE_CXX_COMPILE_FEATURES)
+            check_cxx_compiler_flag("${SANITIZER_ARGS}" "CXX_HAS_SAN_ARGS")
+        endif()
         if (NOT ${C_HAS_SAN_ARGS} OR NOT ${CXX_HAS_SAN_ARGS})
             message(FATAL_ERROR "sanitizer argument ${SANITIZER_ARGS} is not supported (either by C or CXX compiler)")
         endif()