diff --git a/llvm/cmake/modules/FindTerminfo.cmake b/llvm/cmake/modules/FindTerminfo.cmake
--- a/llvm/cmake/modules/FindTerminfo.cmake
+++ b/llvm/cmake/modules/FindTerminfo.cmake
@@ -15,11 +15,11 @@

 if(Terminfo_LIBRARIES)
   include(CMakePushCheckState)
-  include(CheckCSourceCompiles)
+  include(CheckCXXSourceCompiles)
   cmake_push_check_state()
   list(APPEND CMAKE_REQUIRED_LIBRARIES ${Terminfo_LIBRARIES})
-  check_c_source_compiles("
-    int setupterm(char *term, int filedes, int *errret);
+  check_cxx_source_compiles("
+    extern \"C\" { int setupterm(char *term, int filedes, int *errret); }
     int main() { return setupterm(0, 0, 0); }"
     Terminfo_LINKABLE)
   cmake_pop_check_state()