Add DVLOG macro to discard logs on user builds

PiperOrigin-RevId: 273740308

tensorflow/core/platform/default/logging.h

@@ -42,7 +42,7 @@ namespace internal {
 class LogMessage : public std::basic_ostringstream<char> {
  public:
   LogMessage(const char* fname, int line, int severity);
-  ~LogMessage();
+  ~LogMessage() override;
 
   // Returns the minimum log level for VLOG statements.
   // E.g., if MinVLogLevel() is 2, then VLOG(2) statements will produce output,
@@ -81,7 +81,14 @@ struct Voidifier {
 class LogMessageFatal : public LogMessage {
  public:
   LogMessageFatal(const char* file, int line) TF_ATTRIBUTE_COLD;
-  TF_ATTRIBUTE_NORETURN ~LogMessageFatal();
+  TF_ATTRIBUTE_NORETURN ~LogMessageFatal() override;
+};
+
+// LogMessageNull supports the DVLOG macro by simply dropping any log messages.
+class LogMessageNull : public std::basic_ostringstream<char> {
+ public:
+  LogMessageNull() {}
+  ~LogMessageNull() override {}
 };
 
 #define _TF_LOG_INFO \
@@ -123,6 +130,15 @@ class LogMessageFatal : public LogMessage {
           ::tensorflow::internal::LogMessage(__FILE__, __LINE__, \
                                              tensorflow::INFO)
 
+// `DVLOG` behaves like `VLOG` in debug mode (i.e. `#ifndef NDEBUG`).
+// Otherwise, it compiles away and does nothing.
+#ifndef NDEBUG
+#define DVLOG VLOG
+#else
+#define DVLOG(verbose_level) \
+  while (false && (verbose_level) > 0) ::tensorflow::internal::LogMessageNull()
+#endif
+
 // CHECK dies with a fatal error if condition is not true.  It is *not*
 // controlled by NDEBUG, so the check will be executed regardless of
 // compilation mode.  Therefore, it is safe to do things like:

tensorflow/core/platform/logging_test.cc

@@ -24,6 +24,8 @@ TEST(Logging, Log) {
   LOG(ERROR) << "Error message";
   VLOG(1) << "A VLOG message";
   VLOG(2) << "A higher VLOG message";
+  DVLOG(1) << "A DVLOG message";
+  DVLOG(2) << "A higher DVLOG message";
 }
 
 TEST(Logging, CheckChecks) {