CheckCompilerFlag: Add Swift Support

Plumb through Swift `check_compiler_flag` support.
Add tests to check that valid flags work and invalid flags don't.

Modules/Internal/CheckFlagCommonConfig.cmake

@@ -48,6 +48,8 @@ macro(CMAKE_CHECK_FLAG_COMMON_INIT _FUNC _LANG _SRC _PATTERNS)
       FAIL_REGEX "argument unused during compilation: .*") # Clang
   elseif("${_LANG}" STREQUAL "ISPC")
     set(${_SRC} "float func(uniform int32, float a) { return a / 2.25; }")
+  elseif("${_LANG}" STREQUAL "Swift")
+    set(${_SRC} "func blarpy() { }")
   else()
     message (SEND_ERROR "${_FUNC}: ${_LANG}: unknown language.")
     return()

Tests/RunCMake/CMakeLists.txt

@@ -703,7 +703,8 @@ add_RunCMake_test(target_sources)
 add_RunCMake_test(CheckCompilerFlag   -DCMake_TEST_CUDA=${CMake_TEST_CUDA}
                                       -DCMake_TEST_ISPC=${CMake_TEST_ISPC}
                                       -DCMAKE_Fortran_COMPILER_ID=${CMAKE_Fortran_COMPILER_ID}
-                                      -DCMake_TEST_HIP=${CMake_TEST_HIP})
+                                      -DCMake_TEST_HIP=${CMake_TEST_HIP}
+                                      -DCMake_TEST_Swift=${CMake_TEST_Swift})
 add_RunCMake_test(CheckSourceCompiles -DCMake_TEST_CUDA=${CMake_TEST_CUDA}
                                       -DCMake_TEST_ISPC=${CMake_TEST_ISPC}
                                       -DCMAKE_Fortran_COMPILER_ID=${CMAKE_Fortran_COMPILER_ID}

Tests/RunCMake/CheckCompilerFlag/CheckCompilerFlagSwift.cmake

@@ -0,0 +1,21 @@
+enable_language (Swift)
+include(CheckCompilerFlag)
+
+set(Swift 1)
+
+# test that the check uses an isolated locale
+set(_env_LC_ALL "${LC_ALL}")
+set(ENV{LC_ALL} "BAD")
+
+check_compiler_flag(Swift "-foo-as-blarpy" SHOULD_FAIL)
+if(SHOULD_FAIL)
+  message(SEND_ERROR "invalid Swift compile flag didn't fail.")
+endif()
+
+check_compiler_flag(Swift "-parseable-output" SHOULD_WORK)
+if(NOT SHOULD_WORK)
+  message(SEND_ERROR "Swift compiler flag '-parseable-output' check failed")
+endif()
+
+# Reset locale
+set(ENV{LC_ALL} ${_env_LC_ALL})

Tests/RunCMake/CheckCompilerFlag/RunCMakeTest.cmake

@@ -32,3 +32,7 @@ endif()
 if(APPLE)
   run_cmake(HeaderpadWorkaround)
 endif()
+
+if(CMake_TEST_Swift)
+  run_cmake(CheckCompilerFlagSwift)
+endif()