Allow using system glog.

CMakeLists.txt

@@ -6,25 +6,57 @@ catkin_simple()
 
 include(ExternalProject)
 
-file(MAKE_DIRECTORY ${CATKIN_DEVEL_PREFIX}/include)
-
-set(VERSION 0.3.5)
-ExternalProject_Add(glog_src
-  URL https://github.com/google/glog/archive/v${VERSION}.zip
-  UPDATE_COMMAND ""
-  PATCH_COMMAND patch -p0 < ${CMAKE_CURRENT_SOURCE_DIR}/fix-unused-typedef-warning.patch
-  CONFIGURE_COMMAND cd ../glog_src/ && autoreconf -fi && ./configure --with-pic
-    --with-gflags=${gflags_catkin_PREFIX}
-    --prefix=${CATKIN_DEVEL_PREFIX}
-  BUILD_COMMAND cd ../glog_src/ && make -j 8
-  INSTALL_COMMAND cd ../glog_src/ && make install -j 8
-)
-
-install(DIRECTORY ${CATKIN_DEVEL_PREFIX}/include/glog
-        DESTINATION ${CATKIN_GLOBAL_INCLUDE_DESTINATION}
-        FILES_MATCHING PATTERN "*.h")
-install(DIRECTORY ${CATKIN_DEVEL_PREFIX}/lib/
-        DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
-        FILES_MATCHING PATTERN "libglog*")
-cs_export(INCLUDE_DIRS ${CATKIN_DEVEL_PREFIX}/include
-          LIBRARIES glog)
+cmake_policy(SET CMP0053 OLD)
+include(cmake/glog-catkin-extras.cmake.in)
+
+# We can't check version numbers easily as the GLOG script doesn't export them.
+
+# If set to OFF, will compile the given version of Glog.
+# If set to ON, will use the system version of Glog.
+# If set to AUTO, will try to use the syste version if there is one, and build otherwise.
+set(USE_SYSTEM_GLOG "AUTO" CACHE INTERNAL "Whether to use the system version of Glog.")
+
+# Check if the version is suitable, otherwise force downloading the newer one.
+if(USE_SYSTEM_GLOG STREQUAL "AUTO")
+  find_package(Glog QUIET)
+  if(GLOG_FOUND)
+    set(USE_SYSTEM_GLOG "ON")
+    message(STATUS "Suitable Glog version found.")
+  else()
+    set(USE_SYSTEM_GLOG "OFF")
+    message(STATUS "No suitable Glog version found.")
+  endif()
+endif()
+
+
+if(USE_SYSTEM_GLOG STREQUAL "OFF")
+  message(STATUS "Installing Glog from source!")
+
+  file(MAKE_DIRECTORY ${CATKIN_DEVEL_PREFIX}/include)
+
+  set(VERSION 0.3.5)
+  ExternalProject_Add(glog_src
+    URL https://github.com/google/glog/archive/v${VERSION}.zip
+    UPDATE_COMMAND ""
+    PATCH_COMMAND patch -p0 < ${CMAKE_CURRENT_SOURCE_DIR}/fix-unused-typedef-warning.patch
+    CONFIGURE_COMMAND cd ../glog_src/ && autoreconf -fi && ./configure --with-pic
+      --with-gflags=${gflags_catkin_PREFIX}
+      --prefix=${CATKIN_DEVEL_PREFIX}
+    BUILD_COMMAND cd ../glog_src/ && make -j 8
+    INSTALL_COMMAND cd ../glog_src/ && make install -j 8
+  )
+
+  install(DIRECTORY ${CATKIN_DEVEL_PREFIX}/include/glog
+          DESTINATION ${CATKIN_GLOBAL_INCLUDE_DESTINATION}
+          FILES_MATCHING PATTERN "*.h")
+  install(DIRECTORY ${CATKIN_DEVEL_PREFIX}/lib/
+          DESTINATION ${CATKIN_PACKAGE_LIB_DESTINATION}
+          FILES_MATCHING PATTERN "libglog*")
+  cs_export(INCLUDE_DIRS ${CATKIN_DEVEL_PREFIX}/include
+            LIBRARIES glog)
+else()
+  message(STATUS "Using system Glog.")
+  cs_install()
+  cs_export(INCLUDE_DIRS  ${GLOG_INCLUDE_DIRS}
+            LIBRARIES     ${GLOG_LIBRARIES})
+endif()