fix issue #516

CMakeLists.txt

@@ -151,13 +151,15 @@ configure_file(tinyxml2.pc.in tinyxml2.pc @ONLY)
 install(FILES ${CMAKE_CURRENT_BINARY_DIR}/tinyxml2.pc DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig)
 
 # uninstall target
-configure_file(
-    "${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
-    "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
-    IMMEDIATE @ONLY)
-
-add_custom_target(uninstall
-    COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+if(NOT TARGET uninstall)
+  configure_file(
+      "${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake.in"
+      "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
+      IMMEDIATE @ONLY)
+
+  add_custom_target(uninstall
+      COMMAND ${CMAKE_COMMAND} -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake)
+endif()
 
 file(WRITE
     ${CMAKE_BINARY_DIR}/${CMAKE_PROJECT_NAME}Config.cmake