protobuf serializetocodedstream returns "false" - c++

Question

I am trying to serialize my Protocol Buffer message in Windows platform and my coding language is C++. After serialization is done it returns "false". Please find the below code and let me know where I am going wrong.
Proto file
message mobile_list{
required string name = 1;
required DeviceType type = 2;
required string imei = 3;
required bytes wifiAddress = 4;
optional bytes macAddress = 5;
}
Protocol buffer Code
#include <unistd.h>
#include "mobile.pb.h"
#include <iostream>
#include <google/protobuf/message.h>
#include <google/protobuf/descriptor.h>
#include <google/protobuf/io/zero_copy_stream_impl.h>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
using namespace google::protobuf::io;
using namespace std;
int main(int argv, char** argc){
mobile payload;
payload.set_name("Testing");
payload.set_type(mobile::Android);
payload.set_imei("123456");
payload.set_wifiAddress("96-00-OM-1E-4R-99");
payload.set_macAddress("96-00-OM-1E-4R-99");
int siz = payload.ByteSize();
char *pkt = new char [siz];
google::protobuf::io::ArrayOutputStream as(pkt,siz);
CodedOutputStream *coded_output = new CodedOutputStream(&as);
coded_output->WriteVarint32(payload.ByteSize());
payload.SerializeToCodedStream(coded_output);
return a.exec();
}

Answer 1

You are allocating a buffer equal to the size of the message (payload.ByteSize()), but then you are trying to write into it a varint followed by the actual message. This adds up to more than the message size. The serialization is failing because it ran out of space.
You should do:
int siz = payload.ByteSize();
siz += CodedOutputStream::VarintSize32(siz);
// ... continue as before ...
Also, on an unrelated note, you are calling ByteSize() multiple times, which is wasteful because the whole message has to be scanned and counted each time. Instead, you should keep a copy of the original size to reuse.