adding -Werror=unused-result compilation flag

Change-Id: I2869d0a150918ad56cefed07d278cbcc6ef5a4b4

cmake_modules/env.cmake

@@ -50,6 +50,7 @@ set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-threadsafe-statics" )
 set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fmerge-all-constants" )
 set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fms-extensions" )
 set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fmerge-all-constants" )
+set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Werror=unused-result" )
 set ( CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC" )
 
 set ( CMAKE_SHARED_LINKER_FLAGS "-Wl,-Bdynamic -Wl,-z,noexecstack" )

src/util/logger.h

@@ -169,7 +169,7 @@ class Logger {
     if (error_ == false) {
       error_ = true;
       if (session_dir_.empty() == false) {
-          //fopen(std::string(session_dir_ + "error").c_str(), "w");
+        auto x = fopen(std::string(session_dir_ + "error").c_str(), "w"); (void)x;
       }
     }
   }