protobuf SerializeToArray rasie segmentation fault at InternalSerializeWithCachedSizesToArray - c++

Question

To reuse protobuf messages, I firstly allocate it(msg_test,msg_proto), and then send it in an loop(for every loop do something like clear,set,send).
protobuf syntax = "proto3";
Call:
int i=0;
while(true){
SendTestImprove(i++);
usleep(1000*1000);
}
Function:
int SendTestImprove(int count)
{
msg_test->Clear();
msg_test->set_count(count);
msg_proto->Clear();
msg_proto->set_allocated_count(msg_test);
msg_proto->set_tick_count(GetTickCount());
zmq_msg_t zmsg;
int size = msg_proto->ByteSize();
int rc = zmq_msg_init_size(&zmsg,size);
if(rc==0){
try
{
rc = msg_proto->SerializeToArray(zmq_msg_data(&zmsg),size)?0:-1;
}
catch (google::protobuf::FatalException fe)
{
LOGFMTE("PbToZmq error: %s",fe.message().c_str());
}
}
int zsize = zmq_msg_size(&zmsg);
rc = zmq_msg_send(&zmsg,m_pub,0);
zmq_msg_close(&zmsg);
LOGFMTD("zmq_msg_send,size=%d,zsize=%d",rc,zsize);
return 0;
}
The error occurred when i=1, at the line :
rc = msg_proto->SerializeToArray(zmq_msg_data(&zmsg),size)?0:-1;
error info is like:
stopped:segmentation fault,at
InternalWriteMessageNoVirtualToArray
,InternalSerializeWithCachedSizesToArray
Can anyone help?

Answer 1

The likely problem is that you're assigning ownership of msg_test to msg_proto in each iteration of the loop, by calling msg_proto->set_allocated_count(msg_test). The first time you do that it's fine, but then the next time through the loop when you call set_allocated_count() a second time, the proto will delete msg_test and reassign the now dangling pointer. The simplest solution is to avoid calling set_allocated_count() and instead just assign a copy of msg_test, like this:
*msg_proto->mutable_count() = msg_test;