diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -291,6 +291,16 @@
 set(LIBCXX_SYSROOT "${CMAKE_SYSROOT}" CACHE STRING "Use alternate sysroot.")
 set(LIBCXX_GCC_TOOLCHAIN "${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}" CACHE STRING "Use alternate GCC toolchain.")
 
+if(NOT CMAKE_SYSROOT AND LIBCXX_SYSROOT)
+  message(WARNING "LIBCXX_SYSROOT is deprecated, please use CMAKE_SYSROOT instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_TARGET AND LIBCXX_TARGET_TRIPLE)
+  message(WARNING "LIBCXX_TARGET_TRIPLE is deprecated, please use CMAKE_CXX_COMPILER_TARGET instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN AND LIBCXX_GCC_TOOLCHAIN)
+  message(WARNING "LIBCXX_GCC_TOOLCHAIN is deprecated, please use CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN instead")
+endif()
+
 # Feature options -------------------------------------------------------------
 option(LIBCXX_ENABLE_EXCEPTIONS "Use exceptions." ON)
 option(LIBCXX_ENABLE_RTTI "Use run time type information." ON)
diff --git a/libcxxabi/CMakeLists.txt b/libcxxabi/CMakeLists.txt
--- a/libcxxabi/CMakeLists.txt
+++ b/libcxxabi/CMakeLists.txt
@@ -132,6 +132,16 @@
 set(LIBCXXABI_GCC_TOOLCHAIN "${CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN}" CACHE PATH "GCC toolchain for cross compiling.")
 set(LIBCXXABI_SYSROOT "${CMAKE_SYSROOT}" CACHE PATH "Sysroot for cross compiling.")
 
+if(NOT CMAKE_SYSROOT AND LIBCXXABI_SYSROOT)
+  message(WARNING "LIBCXXABI_SYSROOT is deprecated, please use CMAKE_SYSROOT instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_TARGET AND LIBCXXABI_TARGET_TRIPLE)
+  message(WARNING "LIBCXXABI_TARGET_TRIPLE is deprecated, please use CMAKE_CXX_COMPILER_TARGET instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN AND LIBCXXABI_GCC_TOOLCHAIN)
+  message(WARNING "LIBCXXABI_GCC_TOOLCHAIN is deprecated, please use CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN instead")
+endif()
+
 set(LIBCXXABI_LIBCXX_LIBRARY_PATH "" CACHE PATH "The path to libc++ library.")
 set(LIBCXXABI_LIBRARY_VERSION "1.0" CACHE STRING
 "Version of libc++abi. This will be reflected in the name of the shared \
diff --git a/libunwind/CMakeLists.txt b/libunwind/CMakeLists.txt
--- a/libunwind/CMakeLists.txt
+++ b/libunwind/CMakeLists.txt
@@ -110,6 +110,16 @@
 set(LIBUNWIND_TEST_COMPILER_FLAGS "" CACHE STRING
     "Additional compiler flags for test programs.")
 
+if(NOT CMAKE_SYSROOT AND LIBUNWIND_SYSROOT)
+  message(WARNING "LIBUNWIND_SYSROOT is deprecated, please use CMAKE_SYSROOT instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_TARGET AND LIBUNWIND_TARGET_TRIPLE)
+  message(WARNING "LIBUNWIND_TARGET_TRIPLE is deprecated, please use CMAKE_CXX_COMPILER_TARGET instead")
+endif()
+if(NOT CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN AND LIBUNWIND_GCC_TOOLCHAIN)
+  message(WARNING "LIBUNWIND_GCC_TOOLCHAIN is deprecated, please use CMAKE_CXX_COMPILER_EXTERNAL_TOOLCHAIN instead")
+endif()
+
 if (LIBUNWIND_ENABLE_SHARED)
   set(LIBUNWIND_DEFAULT_TEST_CONFIG "llvm-libunwind-shared.cfg.in")
 else()