c – 为什么在dlopen’d函数内传递std :: any的std :: any_cast

我正在玩c 17和插件,我遇到了一个我无法解决的错误.在下面的MWE中,我可以调用一个带有std :: any的本地函数,当我尝试读取内容时,一切都按预期工作.当我通过插件(dlopen)加载这个完全相同的函数时,它正确地看到了any上的类型,但它不能std :: any_cast内容.

在弄清楚导致此错误的原因时,将非常感谢任何帮助.

这是我的环境,MWE和产生的错误.

>> g++ --version

g++ (GCC) 7.1.1 20170526 (Red Hat 7.1.1-2)
Copyright (C) 2017 Free Software Foundation,Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

>> scons --version

SCons by Steven Knight et al.:
    script: v2.5.1.rel_2.5.1:3735:9dc6cee5c168[MODIFIED],2016/11/03 14:02:02,by bdbaddog on mongodog
    engine: v2.5.1.rel_2.5.1:3735:9dc6cee5c168[MODIFIED],by bdbaddog on mongodog
    engine path: ['/usr/lib/scons/SCons']
Copyright (c) 2001 - 2016 The SCons Foundation

>> tree

.
├── SConstruct
└── src
    ├── main.cpp
    ├── plugin.cpp
    └── SConscript

1 directory,4 files

>> cat SConstruct

SConscript('src/SConscript',variant_dir='build',duplicate=0)

>> cat src/SConscript

env = Environment()
env.Append(CXXFLAGS=['-std=c++17'])
plugin = env.SharedLibrary('plugin','plugin.cpp')
Install('../lib',plugin)
driver_env = env.Clone()
driver_env.Append(LIBS=['dl','stdc++fs'])
driver = driver_env.Program('driver','main.cpp')
Install('../bin',driver)

>> cat src/plugin.cpp

#include <any>
#include <iostream>
using namespace std;
extern "C" {
int plugin(any& context) {
    cout << "    Inside Plugin" << endl;
    cout << "    Has Value? " << context.has_value() << endl;
    cout << "    Type Name: " << context.type().name() << endl;
    cout << "    Value: " << any_cast<double>(context) << endl;
}
}

>> cat src/main.cpp

#include <functional>
#include <iostream>
#include <stdexcept>
#include <any>
#include <experimental/filesystem>
#include <dlfcn.h>

using namespace std;
using namespace std::experimental;

function< void(any&) > loadplugin(string filename) {
    function< void(any&) > plugin;
    filesystem::path library_path(filename);
    filesystem::path library_abspath = canonical(library_path);
    void * libraryHandle = dlopen(library_abspath.c_str(),RTLD_NOW);
    if (!libraryHandle) {
        throw runtime_error("ERROR: Could not load the library");
    }
    plugin = (int(*) (any&))dlsym(libraryHandle,"plugin");
    if (!plugin) {
        throw runtime_error("ERROR: Could not load the plugin");
    }
    return plugin;
}

int local(any& context) {
    cout << "    Inside Local" << endl;
    cout << "      Has Value? " << context.has_value() << endl;
    cout << "      Type Name: " << context.type().name() << endl;
    cout << "      Value: " << any_cast<double>(context) << endl;
}

int main(int argc,char* argv[]) {
    cout << "  Resolving Paths..." << endl;
    filesystem::path full_path = filesystem::system_complete( argv[0] ).parent_path();
    filesystem::path plugin_path(full_path/".."/"lib"/"libplugin.so");
    cout << "  Creating Context..." << endl;
    any context(.1);
    cout << "  Loading Plugin..." << endl;
    function<void(any&) > plugin = loadplugin(plugin_path.string());
    cout << "  Calling Local..." << endl;
    local(context);
    cout << "  Calling Plugin..." << endl;
    plugin(context);
}

>> scons

scons: Reading SConscript files ...
scons: done reading SConscript files.
scons: Building targets ...
g++ -o build/main.o -c -std=c++17 src/main.cpp
g++ -o build/driver build/main.o -ldl -lstdc++fs
Install file: "build/driver" as "bin/driver"
g++ -o build/plugin.os -c -std=c++17 -fPIC src/plugin.cpp
g++ -o build/libplugin.so -shared build/plugin.os
Install file: "build/libplugin.so" as "lib/libplugin.so"
scons: done building targets.

>> tree

.
├── bin
│?? └── driver
├── build
│?? ├── driver
│?? ├── libplugin.so
│?? ├── main.o
│?? └── plugin.os
├── lib
│?? └── libplugin.so
├── SConstruct
└── src
    ├── main.cpp
    ├── plugin.cpp
    └── SConscript

4 directories,10 files

>> bin/driver

Resolving Paths...
  Creating Context...
  Loading Plugin...
  Calling Local...
    Inside Local
      Has Value? 1
      Type Name: d
      Value: 0.1
  Calling Plugin...
    Inside Plugin
    Has Value? 1
    Type Name: d
terminate called after throwing an instance of 'std::bad_any_cast'
  what():  bad any_cast
    Value: Aborted (core dumped)