从 .so 导入函数

Question

我需要从带有 boost.dll 库的 Linux .so 库中导入一个函数。我的代码是这样的：

namespace n1 {
    namespace n2 {
        struct st {
            std::string n;
            int m;
        }
    }
}

void foo(std::string const&, n1::n2::st& attr) {
    /*some implementation*/
}

这里我尝试导入函数foo()：

int main(int argc, char** argv) {
    boost::filesystem::path path("some path");
    boost::dll::experimental::smart_library lib(path);
    auto f2 = lib.get_function<void(std::string const&, n1::n2::st&)>(path, "n1::n2::foo");  //<<----here runtime error
    f2( std::string(), st{});
}

但我收到此运行时错误：

在抛出 'boost::exception_detail::clone_impl >' 的实例后调用终止 what(): boost::dll::shared_library::get() failed (dlerror system message: /path_to_my_library.so: undefined symbol: n1::n2::foo): Illegal seek

Answer 1

因为n1::n2::foo 不是与 C 兼容的导出名称，我建议您需要使用损坏的名称，或者使用 mangled_import

注意：此功能是实验性的

在我的编译器上

foo(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, n1::n2::st&)

改成

_Z3fooRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERN2n12n22stE

关于导入结构体的话题，请参阅Class Imports

更新

基于手动修改方法的工作示例：

1. shared.cpp

   #include "shared.h"
   #include <iostream>
   
   void foo(std::string const& msg, n1::n2::st& attr) {
       std::cout << msg << " from " << __FILE__ << ":" << __LINE__ << " (" << __PRETTY_FUNCTION__ << ")\n";
       std::cout << "attr.m = " << attr.m << "\n";
       std::cout << "attr.n = " << attr.n << "\n";
   }
   

2. shared.h

   #include <string>
   namespace n1 { namespace n2 { struct st { std::string n; int m; }; } }
   

3. main.cpp

   #include <boost/dll.hpp>
   #include <boost/dll/smart_library.hpp>
   #include <boost/dll/import_mangled.hpp>
   #include <boost/exception/diagnostic_information.hpp>
   #include <iostream>
   
   #include "shared.h"
   
   int main() {
       boost::filesystem::path path("./libshared.so");
       try {
           boost::dll::experimental::smart_library lib(path);
           //auto f1 = boost::dll::experimental::import_mangled<void(std::string const&, n1::n2::st&)>(path, "foo");
           auto f1 = boost::dll::import<void(std::string const&, n1::n2::st&)>(path, "_Z3fooRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERN2n12n22stE");
   
           n1::n2::st arg { "world", 42 };
           f1("hello", arg);
   
       } catch(boost::exception const& e) {
           std::cout << boost::diagnostic_information(e, true) << '\n';
       }
   }
   

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编译：

g++ -std=c++14 -shared -fPIC shared.cpp -o libshared.so
g++ -std=c++14 main.cpp -ldl -lboost_system -lboost_filesystem

用

显示错位的名字

nm libshared.so

运行演示

./a.out

打印

hello from shared.cpp:5 (void foo(const string&, n1::n2::st&))
attr.m = 42
attr.n = world