boost :: signals2 undefined-reference当链接库在一起 [英] boost::signals2 undefined-reference when linking libraries together
问题描述
我想将两个库链接到我的程序。第一个，定义一个发出信号的对象（ ProducerObject 类）。第二个库定义了两个类：一个包含了ProducerObject 实例的从类和一个可以通过从类预订 ProducerObject 信号的主类。 p>
第一个lib的代码是：
ProducerObject.hpp：
#ifndef PRODUCEROBJECT_HPP_
#define PRODUCEROBJECT_HPP_
#include< boost / shared_ptr.hpp>
#include< boost / signals2.hpp>
#include< boost / function.hpp> //不应该需要
命名空间testnm {
类ProducerObject {
public：
typedef boost :: signals2 ::信号< void（boost :: shared_ptr< int>）> broadcast_signal_t;
typedef broadcast_signal_t :: slot_type broadcast_slot_t;
private：
broadcast_signal_t sig_;
public：
ProducerObject（）;
virtual〜ProducerObject（）;
boost :: signals2 :: connection connect（const broadcast_slot_t& slot）;
boost :: signals2 :: connection connect2（const boost :: function< void（boost :: shared_ptr< int>）>& slot）; //不应该需要
void sendMessage（boost :: shared_ptr< int> msg）;
};
} / *命名空间testnm * /
#endif / * PRODUCEROBJECT_HPP_ * /
ProducerObject.cpp：
#include ProducerObject.hpp
命名空间testnm {
ProducerObject :: ProducerObject（）{
}
ProducerObject :: 〜ProducerObject（）{
}
boost :: signals2 :: connection ProducerObject :: connect（const broadcast_slot_t& slot）{
return sig_.connect ）;
}
//不应该需要
boost :: signals2 :: connection ProducerObject :: connect2（const boost :: function< void（boost :: shared_ptr< int> ;）& slot）{
return connect（slot）;
}
void ProducerObject :: sendMessage（boost :: shared_ptr< int> msg）{
sig_（msg）;
}
} / *命名空间testnm * /
编译这在与使用命令的代码相同的Debug目录中：
g ++ -O0 - g3 -Wall -c -fmessage-length = 0 -fPIC -MMD -MP -MFProducerObject.d-MTProducerObject.d-oProducerObject.o../ProducerObject.cpp\"
g ++ -shared -olibProducerObject.so./ProducerObject.o
第二个库的代码是：
MasterAPI.hpp：
#ifndef MASTERAPI_HPP_
#define MASTERAPI_HPP_
#includeSlaveAPI.hpp
#include< ProducerObject.hpp>
#include< iostream>
#include< boost / shared_ptr.hpp>
#include< boost / bind.hpp>
命名空间testnm {
class MasterAPI {
private：
int id_;
public：
MasterAPI（const int& id）;
virtual〜MasterAPI（）;
void subscribeToProducer（boost :: shared_ptr< SlaveAPI> slave，const unsigned long int& producerid）;
virtual void onMessage（boost :: shared_ptr< int> msg）;
};
} / *命名空间testnm * /
#endif / * MASTERAPI_HPP_ * /
SlaveAPI.hpp：
#ifndef SLAVEAPI_HPP_
#define SLAVEAPI_HPP_
#include< ProducerObject.hpp>
#include< boost / shared_ptr.hpp>
命名空间testnm {
class MasterAPI; // forward declaration
class SlaveAPI {
public：
SlaveAPI（）;
virtual〜SlaveAPI（）;
virtual boost :: shared_ptr< ProducerObject> getProducer（const unsigned long int& producerid）const = 0;
void sendDedicatedMessage（const boost :: shared_ptr< MasterAPI> master，boost :: shared_ptr< int> msg）;
};
} / *命名空间testnm * /
#includeMasterAPI.hpp//完全声明'MasterAPI'类
//实现方法'sendDedicatedMessage'）
#endif / * SLAVEAPI_HPP_ * /
SlaveBase.hpp：
#ifndef SLAVEBASE_HPP_
#define SLAVEBASE_HPP_
#includeSlaveAPI.hpp
#include< ProducerObject.hpp>
#include< unordered_map>
#include< boost / shared_ptr.hpp>
命名空间testnm {
类SlaveBase：public SlaveAPI {
private：
std :: unordered_map< unsigned long int，boost： ：shared_ptr< ProducerObject> >生产者
public：
SlaveBase（）;
virtual〜SlaveBase（）;
virtual boost :: shared_ptr< ProducerObject> getProducer（const unsigned long int& producerid）const;
};
} / *命名空间testnm * /
#endif / * SLAVEBASE_HPP_ * /
MasterAPI.cpp：
#include MasterAPI.hpp
namespace testnm {
MasterAPI :: MasterAPI（const int& id）：id_（id）{
}
MasterAPI ::〜MasterAPI（）{
}
void MasterAPI :: subscribeToProducer（boost :: shared_ptr< SlaveAPI> slave，const unsigned long int& ; producerid）{
boost :: shared_ptr< ProducerObject> producer = slave-> getProducer（producerid）;
// producer-> connect（（ProducerObject :: broadcast_slot_t）（boost :: bind（& MasterAPI :: onMessage，this，_1） //不应该注释
producer-> connect2（boost :: bind（& MasterAPI :: onMessage，this，_1））; //不应该需要
}
void MasterAPI :: onMessage（boost :: shared_ptr< int> msg）{
std :: cout< 在MasterAPI中接收到的消息（<< id_<）：value =< * msg<< std :: endl;
}
} / *命名空间testnm * /
strong> SlaveAPI.cpp：
#includeSlaveAPI.hpp
namespace testnm {
SlaveAPI :: SlaveAPI（）{
}
SlaveAPI ::〜SlaveAPI（）{
}
void SlaveAPI :: sendDedicatedMessage（const boost :: shared_ptr< MasterAPI> master，boost :: shared_ptr< int> msg）{
master-> onMessage（msg）;
}
} / *命名空间testnm * /
strong> SlaveBase.cpp：
#includeSlaveBase.hpp
命名空间testnm {
SlaveBase :: SlaveBase（）{
boost :: shared_ptr< ProducerObject>生产者（new ProducerObject）;
producer_ [1] = producer;
producer.reset（new ProducerObject）;
producer_ [2] = producer;
}
SlaveBase ::〜SlaveBase（）{
}
boost :: shared_ptr< ProducerObject> SlaveBase :: getProducer（const unsigned long int& producerid）const {
std :: unordered_map< unsigned long int，boost :: shared_ptr< ProducerObject> > :: const_iterator prod_it = producers_.find（producerid）;
if（prod_it == producers_.end（））
return boost :: shared_ptr< ProducerObject>（）;
return prod_it-> second;
}
} / *命名空间testnm * /
编译此代码具有：
g ++ -I/ home / chris / workspace / ProducerObject-O0 -g3 - Wall -c -fmessage-length = 0 -std = c ++ 0x -fPIC -MMD -MP -MFMasterAPI.d-MTMasterAPI.d-oMasterAPI.o../MasterAPI.cpp g ++ -I/ home / chris / workspace / ProducerObject-O0 -g3 -Wall -c -fmessage-length = 0 -std = c ++ 0x -fPIC -MMD -MP -MFSlaveAPI.d-MTSlaveAPI.d-oSlaveAPI.o../SlaveAPI.cpp\"
g ++ -I/ home / chris / workspace / ProducerObject-O0 -g3 -Wall -c -fmessage- length = 0 -std = c ++ 0x -fPIC -MMD -MP -MFSlaveBase.d-MTSlaveBase.d-oSlaveBase.o../SlaveBase.cpp\"
g ++ -L/ home / chris / workspace / ProducerObject / Debug-shared -olibObjectAPI.so./MasterAPI .o ./SlaveAPI.o ./SlaveBase.o -lProducerObject
最后，程序本身：
ObjectTest.cpp：
＃ include< ProducerObject.hpp>
#include< SlaveBase.hpp>
#include< MasterAPI.hpp>
#include< iostream>
#include< boost / shared_ptr.hpp>
使用namespace std;
using namespace testnm;
int main（int argc，char * argv []）{
boost :: shared_ptr< SlaveBase> slave（new SlaveBase）;
boost :: shared_ptr< MasterAPI> master1（new MasterAPI（1）），master2（new MasterAPI（2））;
master1-> subscribeToProducer（slave，1）;
master1-> subscribeToProducer（slave，2）;
master2-> subscribeToProducer（slave，1）;
cout<< - 向master1发送专用消息：< endl;
boost :: shared_ptr< int> msg（new int（11））;
slave-> sendDedicatedMessage（master1，msg）;
cout<< \\\
- >从procuder1发送广播消息：< endl;
boost :: shared_ptr< ProducerObject> producer1 = slave-> getProducer（1）;
msg.reset（new int（22））;
producer1-> sendMessage（msg）;
cout<< \\\
- >从procuder2发送广播消息：< endl;
boost :: shared_ptr< ProducerObject> producer2 = slave-> getProducer（2）;
msg.reset（new int（33））;
producer2-> sendMessage（msg）;
return 0;
}
编译：
< blockquote>
g ++ -I/ home / chris / workspace / ProducerObject-I/ home / chris / workspace / ObjectAPI-O0 -g3 -Wall -c -fmessage -length = 0 -std = c ++ 0x -MMD -MP -MFObjectTest.d-MTObjectTest.d-oObjectTest.o../ObjectTest.cpp\"
g ++ -L/ home / chris / workspace / ProducerObject / Debug-L/ home / chris / workspace / ObjectAPI / Debug -oObjectTest./ObjectTest.o -lObjectAPI -lProducerObject
输出，这正是需要的：
- 向master1发送专用消息：
收到消息在MasterAPI（1）：value = 11
- >从procuder1发送广播消息：
MasterAPI = 22
在MasterAPI（2）中收到的消息：value = 22
- >从procuder2发送广播消息：
在MasterAPI（1）中收到的消息：value = 33
为了产生这个输出，我不得不依赖辅助方法 connect2 ，它采用一个 boost :: function 作为参数。我想避免这一点，因为slot的签名应该已经包含在* broadcast_slot_t *类型中。所以，我想实现的代码版本不会包含 connect2 方法。但是，如果我们在实现方法 MasterAPI :: subscribeToProducer （只需更改要测试的注释）中从 connect2 切换到 connect 编译阶段（一切都链接在一起）会产生以下错误：
> /home/chris/workspace/ObjectAPI/Debug/libObjectAPI.so：未定义的引用`testnm :: ProducerObject :: connect（boost :: signals2 :: slot< void（boost :: shared_ptr< int>），boost :: function< ; void（boost :: shared_ptr< int>）>> const&）'
> collect2：error：ld returned 1 exit status
> make：*** [ObjectTest]错误1
为什么以及如何避免？
为了削减一个长的故事，你不能结合使用 -stdc = c ++ 0x 和那些编译没有，永远。你很幸运得到一个链接器错误，而不是一个神秘的崩溃。
I would like to link two libraries to my program. The first one, defines an object (of class ProducerObject) which emits a signal. The second library defines two classes: a slave class which contains several instances of ProducerObject and a master class which can subscribe to the signals of the ProducerObject throught the slave class.
The code of the first lib is:
ProducerObject.hpp:
#ifndef PRODUCEROBJECT_HPP_
#define PRODUCEROBJECT_HPP_
#include <boost/shared_ptr.hpp>
#include <boost/signals2.hpp>
#include <boost/function.hpp> // shouldn't be needed
namespace testnm {
class ProducerObject {
public:
typedef boost::signals2::signal<void (boost::shared_ptr<int>)> broadcast_signal_t;
typedef broadcast_signal_t::slot_type broadcast_slot_t;
private:
broadcast_signal_t sig_;
public:
ProducerObject();
virtual ~ProducerObject();
boost::signals2::connection connect(const broadcast_slot_t& slot);
boost::signals2::connection connect2(const boost::function<void(boost::shared_ptr<int>)>& slot); // shouldn't be needed
void sendMessage(boost::shared_ptr<int> msg);
};
} /* namespace testnm */
#endif /* PRODUCEROBJECT_HPP_ */
ProducerObject.cpp:
#include "ProducerObject.hpp"
namespace testnm {
ProducerObject::ProducerObject() {
}
ProducerObject::~ProducerObject() {
}
boost::signals2::connection ProducerObject::connect(const broadcast_slot_t& slot) {
return sig_.connect(slot);
}
// shouldn't be needed
boost::signals2::connection ProducerObject::connect2(const boost::function<void(boost::shared_ptr<int>)>& slot) {
return connect(slot);
}
void ProducerObject::sendMessage(boost::shared_ptr<int> msg) {
sig_(msg);
}
} /* namespace testnm */
Compile this in a Debug directory which is at the same level as the code with the command:
g++ -O0 -g3 -Wall -c -fmessage-length=0 -fPIC -MMD -MP -MF"ProducerObject.d" -MT"ProducerObject.d" -o "ProducerObject.o" "../ProducerObject.cpp"
g++ -shared -o "libProducerObject.so" ./ProducerObject.o
The code of the second library is:
MasterAPI.hpp:
#ifndef MASTERAPI_HPP_
#define MASTERAPI_HPP_
#include "SlaveAPI.hpp"
#include <ProducerObject.hpp>
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/bind.hpp>
namespace testnm {
class MasterAPI {
private:
int id_;
public:
MasterAPI(const int& id);
virtual ~MasterAPI();
void subscribeToProducer(boost::shared_ptr<SlaveAPI> slave, const unsigned long int& producerid);
virtual void onMessage(boost::shared_ptr<int> msg);
};
} /* namespace testnm */
#endif /* MASTERAPI_HPP_ */
SlaveAPI.hpp:
#ifndef SLAVEAPI_HPP_
#define SLAVEAPI_HPP_
#include <ProducerObject.hpp>
#include <boost/shared_ptr.hpp>
namespace testnm {
class MasterAPI; // forward declaration
class SlaveAPI {
public:
SlaveAPI();
virtual ~SlaveAPI();
virtual boost::shared_ptr<ProducerObject> getProducer(const unsigned long int& producerid) const = 0;
void sendDedicatedMessage(const boost::shared_ptr<MasterAPI> master, boost::shared_ptr<int> msg);
};
} /* namespace testnm */
#include "MasterAPI.hpp" // full declaration of the 'MasterAPI' class
// (used in the implementation of the method 'sendDedicatedMessage')
#endif /* SLAVEAPI_HPP_ */
SlaveBase.hpp:
#ifndef SLAVEBASE_HPP_
#define SLAVEBASE_HPP_
#include "SlaveAPI.hpp"
#include <ProducerObject.hpp>
#include <unordered_map>
#include <boost/shared_ptr.hpp>
namespace testnm {
class SlaveBase : public SlaveAPI {
private:
std::unordered_map<unsigned long int, boost::shared_ptr<ProducerObject> > producers_;
public:
SlaveBase();
virtual ~SlaveBase();
virtual boost::shared_ptr<ProducerObject> getProducer(const unsigned long int& producerid) const;
};
} /* namespace testnm */
#endif /* SLAVEBASE_HPP_ */
MasterAPI.cpp:
#include "MasterAPI.hpp"
namespace testnm {
MasterAPI::MasterAPI(const int& id) :id_(id) {
}
MasterAPI::~MasterAPI() {
}
void MasterAPI::subscribeToProducer(boost::shared_ptr<SlaveAPI> slave, const unsigned long int& producerid) {
boost::shared_ptr<ProducerObject> producer = slave->getProducer(producerid);
//producer->connect((ProducerObject::broadcast_slot_t)(boost::bind(&MasterAPI::onMessage, this, _1))); // shouldn't be commented
producer->connect2(boost::bind(&MasterAPI::onMessage, this, _1)); // shouldn't be needed
}
void MasterAPI::onMessage(boost::shared_ptr<int> msg) {
std::cout << "Message received in MasterAPI(" << id_ << "): value = " << *msg << std::endl;
}
} /* namespace testnm */
SlaveAPI.cpp:
#include "SlaveAPI.hpp"
namespace testnm {
SlaveAPI::SlaveAPI() {
}
SlaveAPI::~SlaveAPI() {
}
void SlaveAPI::sendDedicatedMessage(const boost::shared_ptr<MasterAPI> master, boost::shared_ptr<int> msg) {
master->onMessage(msg);
}
} /* namespace testnm */
SlaveBase.cpp:
#include "SlaveBase.hpp"
namespace testnm {
SlaveBase::SlaveBase() {
boost::shared_ptr<ProducerObject> producer(new ProducerObject);
producers_[1] = producer;
producer.reset(new ProducerObject);
producers_[2] = producer;
}
SlaveBase::~SlaveBase() {
}
boost::shared_ptr<ProducerObject> SlaveBase::getProducer(const unsigned long int& producerid) const {
std::unordered_map<unsigned long int, boost::shared_ptr<ProducerObject> >::const_iterator prod_it = producers_.find(producerid);
if (prod_it == producers_.end())
return boost::shared_ptr<ProducerObject>();
return prod_it->second;
}
} /* namespace testnm */
Compile this code with:
g++ -I"/home/chris/workspace/ProducerObject" -O0 -g3 -Wall -c -fmessage-length=0 -std=c++0x -fPIC -MMD -MP -MF"MasterAPI.d" -MT"MasterAPI.d" -o "MasterAPI.o" "../MasterAPI.cpp"
g++ -I"/home/chris/workspace/ProducerObject" -O0 -g3 -Wall -c -fmessage-length=0 -std=c++0x -fPIC -MMD -MP -MF"SlaveAPI.d" -MT"SlaveAPI.d" -o "SlaveAPI.o" "../SlaveAPI.cpp"
g++ -I"/home/chris/workspace/ProducerObject" -O0 -g3 -Wall -c -fmessage-length=0 -std=c++0x -fPIC -MMD -MP -MF"SlaveBase.d" -MT"SlaveBase.d" -o "SlaveBase.o" "../SlaveBase.cpp"
g++ -L"/home/chris/workspace/ProducerObject/Debug" -shared -o "libObjectAPI.so" ./MasterAPI.o ./SlaveAPI.o ./SlaveBase.o -lProducerObject
Finally, the programm itself:
ObjectTest.cpp:
#include <ProducerObject.hpp>
#include <SlaveBase.hpp>
#include <MasterAPI.hpp>
#include <iostream>
#include <boost/shared_ptr.hpp>
using namespace std;
using namespace testnm;
int main(int argc, char* argv[]) {
boost::shared_ptr<SlaveBase> slave(new SlaveBase);
boost::shared_ptr<MasterAPI> master1(new MasterAPI(1)), master2(new MasterAPI(2));
master1->subscribeToProducer(slave, 1);
master1->subscribeToProducer(slave, 2);
master2->subscribeToProducer(slave, 1);
cout << "--> sending a dedicated message to master1:" << endl;
boost::shared_ptr<int> msg(new int(11));
slave->sendDedicatedMessage(master1, msg);
cout << "\n--> sending a broadcast message from procuder1:" << endl;
boost::shared_ptr<ProducerObject> producer1 = slave->getProducer(1);
msg.reset(new int(22));
producer1->sendMessage(msg);
cout << "\n--> sending a broadcast message from procuder2:" << endl;
boost::shared_ptr<ProducerObject> producer2 = slave->getProducer(2);
msg.reset(new int(33));
producer2->sendMessage(msg);
return 0;
}
Compile with:
g++ -I"/home/chris/workspace/ProducerObject" -I"/home/chris/workspace/ObjectAPI" -O0 -g3 -Wall -c -fmessage-length=0 -std=c++0x -MMD -MP -MF"ObjectTest.d" -MT"ObjectTest.d" -o "ObjectTest.o" "../ObjectTest.cpp"
g++ -L"/home/chris/workspace/ProducerObject/Debug" -L"/home/chris/workspace/ObjectAPI/Debug" -o "ObjectTest" ./ObjectTest.o -lObjectAPI -lProducerObject
This program produces the following output, which is exactly what is wanted:
--> sending a dedicated message to master1:
Message received in MasterAPI(1): value = 11--> sending a broadcast message from procuder1:
Message received in MasterAPI(1): value = 22
Message received in MasterAPI(2): value = 22--> sending a broadcast message from procuder2:
Message received in MasterAPI(1): value = 33
To produce this output, I had to rely on the auxiliary method connect2 which takes a boost::function as argument. I would like to avoid this as the signature of the slot should already be contained in the *broadcast_slot_t* type. So, the version of the code I would like to achieve would not contain the connect2 method. But if I switch from connect2 to connect in the implementation of the method MasterAPI::subscribeToProducer (simply change the comments to test), the last compilation phase (where everything is linked together) produces the following error:
> /home/chris/workspace/ObjectAPI/Debug/libObjectAPI.so: undefined reference to `testnm::ProducerObject::connect(boost::signals2::slot<void (boost::shared_ptr<int>), boost::function<void (boost::shared_ptr<int>)> > const&)'
> collect2: error: ld returned 1 exit status
> make: *** [ObjectTest] Error 1
Why and how to avoid it?
To cut a long story short, you cannot combine objects compiled with -stdc=c++0x and those compiled without, ever. You are lucky to get a linker error instead of a mysterious crash.
这篇关于boost :: signals2 undefined-reference当链接库在一起的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
