When serializing to an ostream, verify that there were no stream-level errors before returning success.

src/google/protobuf/message.cc

@@ -168,8 +168,11 @@ bool Message::SerializePartialToFileDescriptor(int file_descriptor) const {
 }
 
 bool Message::SerializeToOstream(ostream* output) const {
+  {
     io::OstreamOutputStream zero_copy_output(output);
-  return SerializeToZeroCopyStream(&zero_copy_output);
+    if (!SerializeToZeroCopyStream(&zero_copy_output)) return false;
+  }
+  return output->good();
 }
 
 bool Message::SerializePartialToOstream(ostream* output) const {

src/google/protobuf/message_unittest.cc

@@ -43,6 +43,7 @@
 #include <unistd.h>
 #endif
 #include <sstream>
+#include <fstream>
 
 #include <google/protobuf/stubs/common.h>
 #include <google/protobuf/io/zero_copy_stream_impl.h>
@@ -77,9 +78,9 @@ TEST(MessageTest, SerializeHelpers) {
   string str1("foo");
   string str2("bar");
 
-  message.SerializeToString(&str1);
-  message.AppendToString(&str2);
-  message.SerializeToOstream(&stream);
+  EXPECT_TRUE(message.SerializeToString(&str1));
+  EXPECT_TRUE(message.AppendToString(&str2));
+  EXPECT_TRUE(message.SerializeToOstream(&stream));
 
   EXPECT_EQ(str1.size() + 3, str2.size());
   EXPECT_EQ("bar", str2.substr(0, 3));
@@ -95,6 +96,14 @@ TEST(MessageTest, SerializeHelpers) {
 
 }
 
+TEST(MessageTest, SerializeToBrokenOstream) {
+  ofstream out;
+  protobuf_unittest::TestAllTypes message;
+  message.set_optional_int32(123);
+
+  EXPECT_FALSE(message.SerializeToOstream(&out));
+}
+
 TEST(MessageTest, ParseFromFileDescriptor) {
   string filename = TestSourceDir() +
                     "/google/protobuf/testdata/golden_message";