C++在Linux平台上加载共享库并在运行时提取类实现

Question

在C++中,是否可以在执行时加载共享库？

我希望用户选择在运行时加载哪个共享库,而无需重新编译整个程序.

dlopen() 是C的解决方案,但我的程序是用C++/Qt编写的,要提取的符号是Qt风格的类,是否有更多的"c ++"方法.

Answer 1

你可以用QLibrary两种方式在Qt中完成它.以下示例以两种不同的方式在运行时从共享库调用函数:

#include <QLibrary>
#include <QDebug>

class  Dynamic_library
{
public:
    Dynamic_library();
    virtual int sum( int len, int * data );
};

typedef Dynamic_library * (*get_object_func)();
typedef int (*call_sum_func)(int len , int * data);

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QLibrary library( "./dynamic_library" );
    library.load();
    if( !library.isLoaded() )
    {
        qDebug() << "Cannot load library.";
        return 0;
    }
    call_sum_func call_sum = (call_sum_func)library.resolve( "call_sum" );
    if( call_sum )
    {
        //Dynamic_library * obj=get_object();

        int * a=new int[3];
        a[0]=2;
        a[1]=3;
        a[2]=4;
        qDebug() << "sum of 2+3+4' = " << call_sum( 3, a ) <<"\n";

        delete [] a;
    }

    get_object_func get_object = (get_object_func)library.resolve( "get_object" );
    if( get_object )
    {
        Dynamic_library * obj=get_object();

        int * a=new int[3];
        a[0]=7;
        a[1]=8;
        a[2]=9;
        qDebug() << "sum of 7+8+9' = " << obj->sum(3, a );

        delete [] a;
    }

    return a.exec();
}

共享库的代码如下:

class DYNAMIC_LIBRARYSHARED_EXPORT Dynamic_library
{
public:
    Dynamic_library();
    virtual int sum( int len, int * data );
};

extern "C" Q_DECL_EXPORT Dynamic_library * get_object()
{
     return new Dynamic_library();
}

extern "C" Q_DECL_EXPORT int call_sum(int len, int * data)
{
     return Dynamic_library().sum(len,data);
}


Dynamic_library::Dynamic_library()
{

}

int Dynamic_library::sum( int len, int *data )
{
    int sum = 0;
    for(int i=0; i<len; ++i )
        sum += data[i];

    return sum;
}