dynamic_cast来自由lt_dlopen（libtool）加载的共享库的接口不工作 [英] dynamic_cast an interface from a shared library which was loaded by lt_dlopen(libtool) doesn't work

问题描述

这是关于我的程序中的插件功能。我需要一个C ++类（和对象）在一个插件可以由主模块通过接口使用。
接口继承如下：

This is about plugin features in my program. I need a C++ class(and object) in a plugin could be used by main module through an interface. The interface inheritance like this:

typedef struct _rwd_plugin_root_t RWD_PLUGIN_ROOT_T;

struct RWD_PLUGIN_API _rwd_plugin_root_t
{
    virtual int add_ref() = 0;
    virtual int release() = 0;
}; 

typedef struct _rwd_plugin_base_t RWD_PLUGIN_BASE_T;

struct RWD_PLUGIN_API _rwd_plugin_base_t : _rwd_plugin_root_t
{
    virtual RWD_PLUGIN_TYPE_T get_plugin_type() = 0;
    virtual const char * get_plugin_label_a() = 0;
    virtual const wchar_t * get_plugin_label_w() = 0;
};

typedef struct _rwd_autocomplete_plugin_base_t RWD_AUTOCOMPLETE_PLUGIN_BASE_T;

struct RWD_PLUGIN_API _rwd_autocomplete_plugin_base_t : _rwd_plugin_base_t
{
    virtual int set_proxy(int type, const char * host, long port) = 0;
    virtual int set_term(const char * text) = 0;
    virtual int set_term(const wchar_t * text) = 0;
    virtual int get_phon(std::vector<std::string> & phons) = 0;
... // omitted it's too long
};

然后我在插件中有一个类来实现这样的接口：

Then I have a class in plugin to implement the interface like this:

class RWD_PLUGIN_API _rwd_dictcn_t : public _rwd_autocomplete_plugin_base_t
{
public:
    _rwd_dictcn_t();
    ~_rwd_dictcn_t();
... // details of implementation omitted

插件中的创建者定义如下：

The creator in plugin is defined like this:

EXTERN_C int RWD_PLUGIN_API create_rwd_plugin(_rwd_plugin_base_t ** pp)
{
    *pp = new _rwd_dictcn_t();
    return OK;
}

最后，我使用主应用程序中的创建者，像这样：

At last, I use the creator in main application so as to use the plugin like this:

...
    lt_dlhandle lh = lt_dlopen(filePath);
        RWD_PLUGIN_CREATE_FUNC_T pPluginFunc = NULL;
        if(lh)
        {
            pPluginFunc = reinterpret_cast<RWD_PLUGIN_CREATE_FUNC_T>(lt_dlsym(lh, "create_rwd_plugin"));

            if(pPluginFunc)
            {
                RWD_PLUGIN_BASE_T * pBase = NULL;
                if(OK == (*pPluginFunc)(&pBase))
                {
                    RWD_PLUGIN_TYPE_T pluginType = pBase->get_plugin_type();
                    if(pluginType == RWD_PLUGIN_TYPE_AUTOCOMPELE)
                    {
...
                        RWD_PLUGIN_FUNC_T pPluginInitFunc = reinterpret_cast<RWD_PLUGIN_FUNC_T>(lt_dlsym(lh, "initialize_rwd_plugin"));
                        if(pPluginInitFunc)
                            (*pPluginInitFunc)(NULL);

                        //  set proxy
                        RWD_AUTOCOMPLETE_PLUGIN_BASE_T * pAuto = dynamic_cast<RWD_AUTOCOMPLETE_PLUGIN_BASE_T*>(pBase);

...

问题是dynamic_cast总是失败，pAuto结束是零。
然而WIN32版本工作正常。
问题发生在linux与autoconf2.61 automake1.10.1 make3.81 g ++ 4.4.4 libtool1.5.26。
我有较少的linux编程经验，希望在这里得到帮助。感谢！

The problem is dynamic_cast always fails and pAuto end up being a nil. However the WIN32 version works fine. The problem happened on linux with autoconf2.61 automake1.10.1 make3.81 g++4.4.4 libtool1.5.26 . I have less experience with linux programming and hope getting help here. Thanks!

如有必要，可以在Sourceforge上获取完整的源代码：
svn co <​​a href =https：//rdwtwdb.svn.sourceforge。 net / svnroot / rdwtwdbrel =nofollow> https://rdwtwdb.svn.sourceforge.net/svnroot/rdwtwdb rdwtwdb

The full source code could be get on Sourceforge if necessary: svn co https://rdwtwdb.svn.sourceforge.net/svnroot/rdwtwdb rdwtwdb

推荐答案

您可以尝试使用 -Wl， - export-dynamic 链接器参数构建。我记得当遇到类似的行为时需要这个参数。

you might try building with -Wl,--export-dynamic linker argument. I recall needing this argument when encountering similar behavior.

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