GTest: make sure also system googletest can be used when building tests if found

Author: Gianfranco Costamagna

CMakeLists.txt

@@ -106,45 +106,54 @@ ADD_DEFINITIONS(
   )
 
 if (LIBSERIAL_ENABLE_TESTING)
+  FIND_PATH(GTEST_SRCPATH src/gtest.cc
+    /usr/src/googletest/googletest
+    /usr/src/googletest
+    /usr/src/gtest
+  )
+  FIND_PACKAGE(GTest)
+  SET(GTEST_DEPENDENCIES)
+  SET(GTestMain gtest gtest_main)
   SET(GTEST_PREFIX "${CMAKE_CURRENT_BINARY_DIR}/gtest")
-
-  EXTERNALPROJECT_ADD(GTestExternal
-     PREFIX             "${GTEST_PREFIX}"
-     URL https://github.com/google/googletest/archive/refs/tags/v1.13.0.tar.gz
-     URL_HASH SHA1=bfa4b5131b6eaac06962c251742c96aab3f7aa78
-     INSTALL_COMMAND ""
-     )
-
-  SET(LIBPREFIX "${CMAKE_STATIC_LIBRARY_PREFIX}")
-  SET(LIBSUFFIX "${CMAKE_STATIC_LIBRARY_SUFFIX}")
-
-  SET(GTEST_LOCATION "${GTEST_PREFIX}/src/GTestExternal-build/lib")
-  SET(GTEST_LIBRARY  "${GTEST_LOCATION}/${LIBPREFIX}gtest${LIBSUFFIX}")
-  SET(GTEST_MAINLIB  "${GTEST_LOCATION}/${LIBPREFIX}gtest_main${LIBSUFFIX}")
-
-  ADD_LIBRARY(GTest IMPORTED STATIC GLOBAL)
-  SET_TARGET_PROPERTIES(GTest
-    PROPERTIES
-    IMPORTED_LOCATION "${GTEST_LIBRARY}"
-    IMPORTED_LINK_INTERFACE_LIBRARIES "${CMAKE_THREAD_LIBS_INIT}"
-    )
-
-  ADD_LIBRARY(GTestMain IMPORTED STATIC GLOBAL)
-  SET_TARGET_PROPERTIES(GTestMain
-    PROPERTIES
-    IMPORTED_LOCATION "${GTEST_MAINLIB}"
-    IMPORTED_LINK_INTERFACE_LIBRARIES "${GTEST_LIBRARY};${CMAKE_THREAD_LIBS_INIT}"
-    )
-
-  ADD_DEPENDENCIES(GTest GTestExternal)
-  ADD_DEPENDENCIES(GTestMain GTestExternal)
-
-  EXTERNALPROJECT_GET_PROPERTY(GTestExternal source_dir)
-
-  INCLUDE_DIRECTORIES(
-    BEFORE ${GTEST_PREFIX}/src/GTestExternal/googletest/include
-    ${Boost_INCLUDE_DIRS}
-    )
+  if(NOT GTEST_FOUND)
+    EXTERNALPROJECT_ADD(GTestExternal
+       PREFIX             "${GTEST_PREFIX}"
+       URL https://github.com/google/googletest/archive/refs/tags/v1.13.0.tar.gz
+       URL_HASH SHA1=bfa4b5131b6eaac06962c251742c96aab3f7aa78
+       INSTALL_COMMAND ""
+       )
+
+    SET(LIBPREFIX "${CMAKE_STATIC_LIBRARY_PREFIX}")
+    SET(LIBSUFFIX "${CMAKE_STATIC_LIBRARY_SUFFIX}")
+
+    SET(GTEST_LOCATION "${GTEST_PREFIX}/src/GTestExternal-build/lib")
+    SET(GTEST_LIBRARY  "${GTEST_LOCATION}/${LIBPREFIX}gtest${LIBSUFFIX}")
+    SET(GTEST_MAINLIB  "${GTEST_LOCATION}/${LIBPREFIX}gtest_main${LIBSUFFIX}")
+
+    ADD_LIBRARY(GTest IMPORTED STATIC GLOBAL)
+    SET_TARGET_PROPERTIES(GTest
+      PROPERTIES
+      IMPORTED_LOCATION "${GTEST_LIBRARY}"
+      IMPORTED_LINK_INTERFACE_LIBRARIES "${CMAKE_THREAD_LIBS_INIT}"
+      )
+
+    ADD_LIBRARY(GTestMain IMPORTED STATIC GLOBAL)
+    SET_TARGET_PROPERTIES(GTestMain
+      PROPERTIES
+      IMPORTED_LOCATION "${GTEST_MAINLIB}"
+      IMPORTED_LINK_INTERFACE_LIBRARIES "${GTEST_LIBRARY};${CMAKE_THREAD_LIBS_INIT}"
+      )
+    SET(GTestMain GTestMain)
+    ADD_DEPENDENCIES(GTest GTestExternal)
+    ADD_DEPENDENCIES(GTestMain GTestExternal)
+
+    EXTERNALPROJECT_GET_PROPERTY(GTestExternal source_dir)
+
+    INCLUDE_DIRECTORIES(
+      BEFORE ${GTEST_PREFIX}/src/GTestExternal/googletest/include
+      ${Boost_INCLUDE_DIRS}
+      )
+  endif()
 endif()
 
 SET(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)

test/CMakeLists.txt

@@ -7,7 +7,7 @@ ADD_EXECUTABLE(UnitTests
 
 TARGET_LINK_LIBRARIES(UnitTests
   libserial_static
-  GTestMain
+  ${GTestMain}
 )
 
 ADD_EXECUTABLE(unit_tests