[XRay] [compiler-rt] [NFC] Annotate unused variables for the compiler.

[pelikan]

Summary

Use a common definition of a "this variable is unused" annotation for useless
variables only present for their lambda global initializers, to silence gcc's
warning.

[dberris]

lib/xray/xray_fdr_logging.cc

526

Where does UNUSED come from?

[pelikan]

sync

[pelikan]

lib/xray/xray_fdr_logging.cc

526

$ git grep UNUSED | grep \#define
lib/builtins/int_lib.h:#define UNUSED
lib/builtins/int_lib.h:#define UNUSED attribute((unused))

This comes from the sanitizer_common header set.

[dberris]

lib/xray/xray_fdr_logging.cc

526

Don't you need to include a header to get that definition?

[dberris]

lib/xray/xray_fdr_logging.cc

526

Apparently not. Landed without further changes after local testing.

lib/xray/xray_fdr_logging.cc

if (auto EC = LocalBQ->releaseBuffer(Buffer)) {
       return;
     }
     RecordPtr = nullptr;
   }
 }
 
 } // namespace __xray
 
-static auto Unused = [] {
+static auto UNUSED Unused = [] {
   using namespace __xray;
   if (flags()->xray_fdr_log) {
     XRayLogImpl Impl{
         fdrLoggingInit, fdrLoggingFinalize, fdrLoggingHandleArg0,
         fdrLoggingFlush,
     };
     __xray_set_log_impl(Impl);
   }
   return true;
 }();

lib/xray/xray_inmemory_log.cc

if (Offset == BuffLen) {
     std::lock_guard<std::mutex> L(LogMutex);
     auto RecordBuffer = reinterpret_cast<__xray::XRayRecord *>(InMemoryBuffer);
     retryingWriteAll(Fd, reinterpret_cast<char *>(RecordBuffer),
                      reinterpret_cast<char *>(RecordBuffer + Offset));
     Offset = 0;
   }
 }
 
-static auto Unused = [] {
+static auto UNUSED Unused = [] {
   if (!probeRequiredCPUFeatures()) {
     Report("Required CPU features missing for XRay instrumentation, not "
            "installing instrumentation hooks.\n");
     return false;
   }
   if (flags()->xray_naive_log)
     __xray_set_handler(__xray_InMemoryRawLog);
   return true;
 }();