[英]c++ static cast with .so loading at run-time
I'm trying to load a shared object ( SensorTemp
derived class) at runtime using the dlopen() API. 我试图在运行时使用dlopen()API加载共享对象(
SensorTemp
派生类)。 When I try to static-case the pointer to the appropriate function pointer, I get 当我尝试将指针静态大小写为适当的函数指针时,我得到
LinkTest.cpp:26:48: error: invalid static_cast from type ‘void*’ to type ‘Sensor*()’
Sensor* mySensor = static_cast<Sensor *()>(mkr)(myHub, a, b, c, d, e);
Here's the relevant Sensor.h
base class constructor: 这是相关的
Sensor.h
基类构造函数:
class Sensor
{
public:
Sensor(Hub& _pHub, const std::string& _name, const std::string& _type, const std::string& _logLevel, const std::string& _configInfo, const std::string& _location): m_pHub(&_pHub), m_name(_name), m_type(_type), m_logLevel(_logLevel), m_configInfo(_configInfo), m_location(_location) {}
Derived class SensorTemp.h
: (its CTOR calls the base CTOR) 派生类
SensorTemp.h
:(其CTOR称为基CTOR)
#include "Sensor.h"
class SensorTemp : public Sensor
{
public:
SensorTemp(Hub& _pHub, const std::string& _name,
const std::string& _type,
const std::string& _logLevel,
const std::string& _configInfo,
const std::string& _location);
~SensorTemp() {}
void* Run();
private:
int m_lowTemp;
int m_highTemp;
int m_interval;
};
extern "C"
{
SensorTemp* Create(Hub& _pHub, const std::string& _name,
const std::string& _type,
const std::string& _logLevel,
const std::string& _configInfo,
const std::string& _location)
{
return new SensorTemp(_pHub, _name, _type, _logLevel, _configInfo, _location);
}
}
#endif //__SENSORTEMP_H__
the test: 考试:
int main(int argc, char **argv)
{
Hub myHub;
string a = "A";
string b = "B";
string c = "C";
string d = "D";
string e = "E";
string f = "F";
void *hndl = dlopen("./libSensorTemp.so", RTLD_LAZY);
if(hndl == NULL)
{
std::cerr << dlerror() << std::endl;
exit(-1);
}
void *mkr = (Sensor*)dlsym(hndl, "Create");
Sensor* mySensor = static_cast<Sensor *()>(mkr)(myHub, a, b, c, d, e);
mySensor->Run();
}
Your cast to a pointer to function is wrong. 您对函数指针的转换是错误的。 Your code should be:
您的代码应为:
void *mkr = (void *)dlsym(hndl, "Create"); // only the address matters here
Sensor* mySensor = static_cast<Sensor *(*)(Hub&, const std::string&, const std::string&,
const std::string&, const std::string&, const std::string&)>(mkr)(myHub, a, b, c, d, e);
mySensor->Run();
Because you want to cast mkr
to a pointer to a function taking one Hub
reference and 5 string
references and returning a pointer to Sensor
因为您想将
mkr
为使用一个Hub
引用和5个string
引用并返回指向Sensor
的函数的指针
In reference to this question , here is a simplified example: 关于此问题 ,这是一个简化的示例:
#include <dlfcn.h>
#include <string>
class Sensor;
class Hub;
extern "C"
{
Sensor* Create(Hub& _pHub
, const std::string& _name
, const std::string& _type
, const std::string& _logLevel
, const std::string& _configInfo
, const std::string& _location)
{
return nullptr;
}
}
int main(int argc, char **argv)
{
void *hndl = dlopen("./libSensorTemp.so", RTLD_LAZY);
if(hndl == NULL) {
exit(-1);
}
void *mkr = (Sensor*)dlsym(hndl, "Create");
typedef Sensor*(*create_fn)(Hub&
, const std::string&
, const std::string&
, const std::string&
, const std::string&
, const std::string&);
create_fn creator = 0;
*reinterpret_cast<void**>(&creator) = mkr;
// ....
}
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