Merge pull request #540 from dalgaaf/wip-da-fix-elif

Fix '#elif with no expression'

port/stack_trace.cc

@@ -71,7 +71,7 @@ void PrintStackTraceLine(const char* symbol, void* frame) {
 
   fprintf(stderr, "\n");
 }
-#elif OS_MACOSX
+#elif defined(OS_MACOSX)
 
 void PrintStackTraceLine(const char* symbol, void* frame) {
   static int pid = getpid();

util/env_posix.cc

@@ -1412,7 +1412,7 @@ class PosixEnv : public Env {
     struct timespec ts;
     clock_gettime(CLOCK_MONOTONIC, &ts);
     return static_cast<uint64_t>(ts.tv_sec) * 1000000000 + ts.tv_nsec;
-#elif __MACH__
+#elif defined(__MACH__)
     clock_serv_t cclock;
     mach_timespec_t ts;
     host_get_clock_service(mach_host_self(), CALENDAR_CLOCK, &cclock);

util/xfunc.h

@@ -20,7 +20,7 @@ namespace rocksdb {
 #if (ROCKSDB_XFTEST_FORCE == 1)
 #define XFUNC
 #endif
-#elif NDEBUG
+#elif defined(NDEBUG)
 #else
 #define XFUNC
 #endif