Simplify CM_FALLTHROUGH implementation

Use the macro now provided by KWSys instead of using `try_compile`
checks.  It will no longer consider the `__attribute__((fallthrough))`
variant, but compilers that don't have one of the modern attributes
shouldn't warn about not using one anyway.

4 files changed, 0 insertions, 40 deletions

diff --git a/Source/Checks/cm_cxx_attribute_fallthrough.cxx b/Source/Checks/cm_cxx_attribute_fallthrough.cxx
deleted file mode 100644
index 50605b70a5..0000000000
--- a/Source/Checks/cm_cxx_attribute_fallthrough.cxx
+++ /dev/null
@@ -1,11 +0,0 @@
-int main(int argc, char* [])
-{
-  int i = 3;
-  switch (argc) {
-    case 1:
-      i = 0;
-      __attribute__((fallthrough));
-    default:
-      return i;
-  }
-}
diff --git a/Source/Checks/cm_cxx_fallthrough.cxx b/Source/Checks/cm_cxx_fallthrough.cxx
deleted file mode 100644
index 2825bed1e9..0000000000
--- a/Source/Checks/cm_cxx_fallthrough.cxx
+++ /dev/null
@@ -1,11 +0,0 @@
-int main(int argc, char* [])
-{
-  int i = 3;
-  switch (argc) {
-    case 1:
-      i = 0;
-      [[fallthrough]];
-    default:
-      return i;
-  }
-}
diff --git a/Source/Checks/cm_cxx_features.cmake b/Source/Checks/cm_cxx_features.cmake
index a30a5e6900..2704c4032a 100644
--- a/Source/Checks/cm_cxx_features.cmake
+++ b/Source/Checks/cm_cxx_features.cmake
@@ -41,13 +41,6 @@ function(cm_check_cxx_feature name)
   endif()
 endfunction()
 
-cm_check_cxx_feature(fallthrough)
-if(NOT CMake_HAVE_CXX_FALLTHROUGH)
-  cm_check_cxx_feature(gnu_fallthrough)
-  if(NOT CMake_HAVE_CXX_GNU_FALLTHROUGH)
-    cm_check_cxx_feature(attribute_fallthrough)
-  endif()
-endif()
 cm_check_cxx_feature(make_unique)
 if(CMake_HAVE_CXX_MAKE_UNIQUE)
   set(CMake_HAVE_CXX_UNIQUE_PTR 1)
diff --git a/Source/Checks/cm_cxx_gnu_fallthrough.cxx b/Source/Checks/cm_cxx_gnu_fallthrough.cxx
deleted file mode 100644
index ebc15f4319..0000000000
--- a/Source/Checks/cm_cxx_gnu_fallthrough.cxx
+++ /dev/null
@@ -1,11 +0,0 @@
-int main(int argc, char* [])
-{
-  int i = 3;
-  switch (argc) {
-    case 1:
-      i = 0;
-      [[gnu::fallthrough]];
-    default:
-      return i;
-  }
-}