mark as unused some variables with cpp-derived names

Summary: as above

Test Plan:
  Run "make EXTRA_CXXFLAGS='-W -Wextra'" and see fewer errors.

Reviewers: ljin, sdong, igor.sugak, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D33753

util/benchharness.h

@@ -154,7 +154,8 @@ AddBenchmark(const char* file, const char* name, Lambda&& lambda) {
 #define FB_CONCATENATE_IMPL(s1, s2) s1##s2
 #define FB_CONCATENATE(s1, s2) FB_CONCATENATE_IMPL(s1, s2)
 
-#define FB_ANONYMOUS_VARIABLE(str) FB_CONCATENATE(str, __LINE__)
+#define FB_ANONYMOUS_VARIABLE(str) \
+  FB_CONCATENATE(str, __LINE__ __attribute__((__unused__)))
 
 #define FB_STRINGIZE(x) #x
 

util/testharness.h

@@ -182,8 +182,9 @@ class TesterHelper {
       t._Run();                                                       \
     }                                                                 \
   };                                                                  \
-  bool TCONCAT(_Test_ignored_, name) = ::rocksdb::test::RegisterTest( \
+  bool TCONCAT(_Test_ignored_, name) __attribute__((__unused__))      \
-      #base, #name, &TCONCAT(_Test_, name)::_RunIt);                  \
+    = ::rocksdb::test::RegisterTest(#base, #name,                     \
+                                    &TCONCAT(_Test_, name)::_RunIt);  \
   void TCONCAT(_Test_, name)::_Run()
 
 // Register the specified test.  Typically not used directly, but