From b2f612a0fabfb87e79b60f440c05a2cecde424f0 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 30 Nov 2017 08:58:01 -0500
Subject: 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.
---
 Source/Checks/cm_cxx_attribute_fallthrough.cxx | 11 -----------
 Source/Checks/cm_cxx_fallthrough.cxx           | 11 -----------
 Source/Checks/cm_cxx_features.cmake            |  7 -------
 Source/Checks/cm_cxx_gnu_fallthrough.cxx       | 11 -----------
 Source/cmConfigure.cmake.h.in                  | 13 +------------
 5 files changed, 1 insertion(+), 52 deletions(-)
 delete mode 100644 Source/Checks/cm_cxx_attribute_fallthrough.cxx
 delete mode 100644 Source/Checks/cm_cxx_fallthrough.cxx
 delete mode 100644 Source/Checks/cm_cxx_gnu_fallthrough.cxx

diff --git a/Source/Checks/cm_cxx_attribute_fallthrough.cxx b/Source/Checks/cm_cxx_attribute_fallthrough.cxx
deleted file mode 100644
index 50605b7..0000000
--- 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 2825bed..0000000
--- 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 a30a5e6..2704c40 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 ebc15f4..0000000
--- 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;
-  }
-}
diff --git a/Source/cmConfigure.cmake.h.in b/Source/cmConfigure.cmake.h.in
index 9a78aca..c80439b 100644
--- a/Source/cmConfigure.cmake.h.in
+++ b/Source/cmConfigure.cmake.h.in
@@ -19,22 +19,11 @@
 #cmakedefine HAVE_UNSETENV
 #cmakedefine CMAKE_USE_ELF_PARSER
 #cmakedefine CMAKE_USE_MACH_PARSER
-#cmakedefine CMake_HAVE_CXX_FALLTHROUGH
-#cmakedefine CMake_HAVE_CXX_GNU_FALLTHROUGH
-#cmakedefine CMake_HAVE_CXX_ATTRIBUTE_FALLTHROUGH
 #cmakedefine CMake_HAVE_CXX_MAKE_UNIQUE
 #define CMAKE_BIN_DIR "/@CMAKE_BIN_DIR@"
 #define CMAKE_DATA_DIR "/@CMAKE_DATA_DIR@"
 
-#if defined(CMake_HAVE_CXX_FALLTHROUGH)
-#define CM_FALLTHROUGH [[fallthrough]]
-#elif defined(CMake_HAVE_CXX_GNU_FALLTHROUGH)
-#define CM_FALLTHROUGH [[gnu::fallthrough]]
-#elif defined(CMake_HAVE_CXX_ATTRIBUTE_FALLTHROUGH)
-#define CM_FALLTHROUGH __attribute__((fallthrough))
-#else
-#define CM_FALLTHROUGH
-#endif
+#define CM_FALLTHROUGH cmsys_FALLTHROUGH
 
 #define CM_DISABLE_COPY(Class)                                                \
   Class(Class const&) = delete;                                               \
-- 
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