Hi all,
Is using virtual destructors fine with a C++ plugin interface?
I have an example below that works. However i am not sure if it is a
good practice. In particular is it ok to make use of virtual
destructors in an application to destroy an object allocated in the
plugin or should I define a pure virtual Destroy() method to ensure
that the actual memory de-allocation (call to delete) is performed in
the plugin where it was also initially allocated?
Thanks,
Brendon.
Compile below using:
g++ -o main -Wall -g -fPIC main.cpp -lltdl
g++ -o myplugin.so -shared -Wall -g -fPIC myimpl.cpp
---- myiface.h ----
class MyIFace
{
public:
virtual ~MyIFace() {}
virtual void DoStuff() = 0;
};
---- myimpl.cpp ----
#include "myiface.h"
#include <iostream>
namespace
{
class MyImpl : public MyIFace
{
public:
MyImpl() :
blah("Hello")
{}
virtual void DoStuff()
{
std::cout << "DoStuff: " << blah << std::endl;
}
private:
std::string blah;
};
}
// For GCC on UNIX
#define MY_CALLTYPE __attribute__((cdecl))
#define MY_EXPORT __attribute__ ((visibility("default")))
extern "C"
{
MY_EXPORT void* MY_CALLTYPE MyFactory(void)
{
return static_cast<void*>(new MyImpl());
}
}
---- main.cpp ----
#include "myiface.h"
#include <iostream>
#include <ltdl.h>
typedef void* (*CreateFP)(void);
int main()
{
lt_dlinit();
lt_dladdsearchdir(".");
lt_dlhandle module = lt_dlopenext("myplugin");
CreateFP create_fp = (CreateFP)lt_dlsym(module, "MyFactory");
MyIFace* iface = static_cast<MyIFace*>(create_fp());
iface->DoStuff();
// Delete the instance!!!!!!!!!!!
// IS THIS A GOOD IDEA?
delete iface;
iface = NULL;
lt_dlclose(module);
lt_dlexit();
return 0;
}
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