Log new ErrorReporter and old nnapi delegate errors to logcat.

On Android stderr is not captured for applications, so developers do not see
the errors from tflite. This adds logcat output.

Output to stderr is kept, as it is convenient for unit tests run through the
shell.

PiperOrigin-RevId: 208463170

tensorflow/contrib/lite/error_reporter.cc

@@ -16,6 +16,10 @@ limitations under the License.
 #include <cstdarg>
 #include <cstdio>
 
+#ifdef __ANDROID__
+#include <android/log.h>
+#endif
+
 namespace tflite {
 
 ErrorReporter::~ErrorReporter() {}
@@ -39,6 +43,15 @@ int ErrorReporter::ReportError(void*, const char* format, ...) {
 }
 
 int StderrReporter::Report(const char* format, va_list args) {
+#ifdef __ANDROID__
+  // On Android stderr is not captured for applications, only for code run from
+  // the shell. Rather than assume all users will set up a custom error
+  // reporter, let's output to logcat here
+  va_list args_for_log;
+  va_copy(args_for_log, args);
+  __android_log_vprint(ANDROID_LOG_ERROR, "tflite", format, args_for_log);
+  va_end(args_for_log);
+#endif
   const int result = vfprintf(stderr, format, args);
   fputc('\n', stderr);
   return result;

tensorflow/contrib/lite/nnapi_delegate.cc

@@ -24,20 +24,27 @@ limitations under the License.
 #include "tensorflow/contrib/lite/nnapi/NeuralNetworksShim.h"
 
 #ifdef __ANDROID__
+#include <android/log.h>
 #include <sys/system_properties.h>
 #endif
 
 namespace tflite {
 
 void logError(const char* format, ...) {
-  // TODO(mikie): use android logging, stderr is not captured for Java
-  // applications
-  va_list args;
-  va_start(args, format);
-  vfprintf(stderr, format, args);
-  va_end(args);
+  // stderr is convenient for native tests, but is not captured for apps
+  va_list args_for_stderr;
+  va_start(args_for_stderr, format);
+  vfprintf(stderr, format, args_for_stderr);
+  va_end(args_for_stderr);
   fprintf(stderr, "\n");
   fflush(stderr);
+#ifdef __ANDROID__
+  // produce logcat output for general consumption
+  va_list args_for_log;
+  va_start(args_for_log, format);
+  __android_log_vprint(ANDROID_LOG_ERROR, "tflite", format, args_for_log);
+  va_end(args_for_log);
+#endif
 }
 
 #define FATAL(...)       \