CPP: Update CMake rules for Google Test to not require a pre-compiled static

library but be able to build the library from source as current practice is.
Review URL: https://codereview.appspot.com/6602047

cpp/CMakeLists.txt

@@ -23,6 +23,8 @@ set (libphonenumber_VERSION_MINOR 1)
 # Helper functions dealing with finding libraries and programs this library
 # depends on.
 
+include (../tools/cpp/gtest.cmake)
+
 function (print_error DESCRIPTION FILE)
   message (FATAL_ERROR
     "Can't find ${DESCRIPTION}: can't locate ${FILE}. Please read the README.")
@@ -82,7 +84,7 @@ if (NOT Boost_FOUND)
 endif ()
 include_directories (${Boost_INCLUDE_DIRS})
 
-find_required_library (GTEST gtest/gtest.h gtest "Google Test framework")
+find_or_build_gtest ()
 
 if (${USE_RE2} STREQUAL "ON")
   find_required_library (RE2 re2/re2.h re2 "Google RE2")

tools/cpp/CMakeLists.txt

@@ -21,32 +21,9 @@ project (generate_geocoding_data)
 # Helper functions dealing with finding libraries and programs this library
 # depends on.
 
-function (print_error DESCRIPTION FILE)
-  message (FATAL_ERROR
-    "Can't find ${DESCRIPTION}: can't locate ${FILE}. Please read the README.")
-endfunction ()
+include (gtest.cmake)
 
-# Find a library. If it has not been found, stop CMake with a fatal error
-# message.
-function (find_required_library NAME HEADER LIBRARY DESCRIPTION)
-  # Check the header.
-  find_path (${NAME}_INCLUDE_DIR ${HEADER})
-  set (INCLUDE_DIR ${${NAME}_INCLUDE_DIR})
-
-  if (${INCLUDE_DIR} STREQUAL "${INCLUDE_DIR}-NOTFOUND")
-    print_error (${DESCRIPTION} ${HEADER})
-  endif ()
-  include_directories (${INCLUDE_DIR})
-  # Check the binary.
-  find_library (${NAME}_LIB ${LIBRARY})
-  set (LIB ${NAME}_LIB)
-
-  if (${LIB} STREQUAL "${LIB}-NOTFOUND")
-    print_error (${DESCRIPTION} ${LIBRARY})
-  endif ()
-endfunction (find_required_library)
-
-find_required_library (GTEST gtest/gtest.h gtest "Google Test framework")
+find_or_build_gtest ()
 
 set (
   SOURCES

tools/cpp/gtest.cmake

@@ -0,0 +1,47 @@
+# Copyright (C) 2012 The Libphonenumber Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Author: Fredrik Roubert
+
+# It used to be common to provide pre-compiled Google Test libraries, but this
+# practice is not recommended and is increasingly rare today:
+#
+# http://code.google.com/p/googletest/wiki/FAQ#Why_is_it_not_recommended_to_install_a_pre-compiled_copy_of_Goog
+#
+# This helper function will either find a pre-compiled library or else find the
+# source code and add a library target to build the library from source.
+
+function (find_or_build_gtest)
+  # Find header files.
+  find_path (GTEST_INCLUDE_DIR gtest/gtest.h)
+  if (${GTEST_INCLUDE_DIR} STREQUAL "GTEST_INCLUDE_DIR-NOTFOUND")
+    message (FATAL_ERROR
+      "Can't find Google C++ Testing Framework: can't locate gtest/gtest.h. "
+      "Please read the README and also take a look at tools/cpp/gtest.cmake.")
+  endif ()
+  include_directories (${GTEST_INCLUDE_DIR})
+
+  # Check for a pre-compiled library.
+  find_library (GTEST_LIB gtest)
+  if (${GTEST_LIB} STREQUAL "GTEST_LIB-NOTFOUND")
+    # No pre-compiled library found, attempt building it from source.
+    find_path (GTEST_SOURCE_DIR src/gtest-all.cc
+               HINTS /usr/src/gtest /usr/local/src/gtest)
+    add_library (gtest STATIC ${GTEST_SOURCE_DIR}/src/gtest-all.cc)
+    include_directories (${GTEST_SOURCE_DIR})
+
+    set (GTEST_LIB gtest PARENT_SCOPE)
+  endif ()
+
+endfunction ()