动态库加载的 C++ 依赖注入

我无法将 C++ 依赖注入库“ boost::di ”与另一个 boost 库一起用于动态加载名为“ Boost.dll ”的库。

我将问题分为两部分 - 首先，测试动态加载，其次，将抽象类绑定到实现（动态加载）。

我能够成功地动态加载库。但是当我尝试使用依赖注入绑定时，它会报告类模板是预期的但未收到的不匹配。

我在这个 repo 中有一个非常基本的示例代码： https ://bitbucket.org/kobe_la/boost-plugins-prework/src/master/

我真的会使用一些帮助来确定动态加载库的绑定过程。（请参阅底部的确切错误）

• ioperation.hpp

   #include 
  
   class ioperation {
  
   public:
       virtual std::string name() const = 0;
       virtual float calculate(float x, float y) = 0;
  
       virtual ~ioperation() {}
   };
  

• 文件sum.cpp

   #include <boost/config.hpp>
   #include <boost/dll/alias.hpp>
   #include <boost/dll/import.hpp>
   #include "ioperation.hpp"
   #include 
  
   namespace sum_namespace {
  
   class sum: public ioperation {
   public:
       sum() {
           std::cout << "[sum_constructor]" << std::endl;
       }
  
       std::string name() const {
           return "sum";
       }
  
       float calculate(float x, float y) {
           return x + y;
       }
  
       ~sum() {
           std::cout << "[~sum_destructor]" << std::endl;
       }
  
  
          // Factory method
           static boost::shared_ptr create_sum() {
                   return boost::shared_ptr(
                           new sum()
                   );
           }
       };
   }
  
   BOOST_DLL_ALIAS(
       sum_namespace::sum::create_sum, // <-- this function is exported with...
       create_sum                                       // <-- ...this alias name
   )
  

• 文件dot_product.cpp

   #include <boost/config.hpp>
   #include <boost/dll/alias.hpp>
   #include <boost/dll/import.hpp>
   #include 
   #include "ioperation.hpp"
  
   namespace dot_product_namespace {
  
   class dot_product: public ioperation {
  
           boost::shared_ptr sum_ptr;
   public:
           dot_product(boost::shared_ptr &arg) {
                   sum_ptr = arg;
                   std::cout << "[dot_product_constructor]" << std::endl;
           }
  
           std::string name() const {
                   return "dot_product";
           }
  
           float calculate(float a1, float a2) {
                   //dot product given vector with itself
                   //formula: a.b = a1*b1 + a2*b2
                   return sum_ptr->calculate(a1*a1, a2*a2);
           }
  
           // Factory method
           static boost::shared_ptr create_dot_product(boost::shared_ptr sum_ptr) {
                   return boost::shared_ptr(
                           new dot_product(sum_ptr)
                   );
           }
  
           ~dot_product() {
                   std::cout << "[~dot_product_destructor]" << std::endl;
           }
       };
   };
  
   BOOST_DLL_ALIAS(
       dot_product_namespace::dot_product::create_dot_product, // <-- this function is exported with...
       create_dot_product                               // <-- ...this alias name
   )
  

• 文件application_di.cpp

   #include "boost/shared_ptr.hpp"
   #include <boost/dll/import.hpp>
   #include "boost/function.hpp"
   #include <boost/di.hpp>
   #include "ioperation.hpp"
   #include 
  
   namespace di = boost::di;
   namespace dll = boost::dll;
  
  
   class app {
    private:
       boost::shared_ptr ptr_;
    public:
       app(boost::shared_ptr ptr)
        : ptr_(ptr)
       {
              std::cout<<"name: " << ptr_->name()<<std::endl;
       }
  
   };
  
  
   int main(int argc, char* argv[]) {
  
       //setting up paths to library(.so) files
           boost::filesystem::path shared_library_path(".");    // argv[1] contains path to directory with our plugin library
           boost::filesystem::path child_library_path = shared_library_path/"dot_product";
           boost::filesystem::path parent_library_path = shared_library_path/"sum";
  
           //defining function types for lib constructors
           typedef boost::shared_ptr (sum_create_t)();
           typedef boost::shared_ptr (dot_product_create_t)(boost::shared_ptr);
           boost::function sum_creator;
           boost::function dot_product_creator;
  
           //importing SUM lib constructor(takes no arg)
           sum_creator = boost::dll::import_alias(   // type of imported symbol must be explicitly specified
                   parent_library_path,                            // path to library
                   "create_sum",                                   // symbol to import
                   dll::load_mode::append_decorations              // do append extensions and prefixes
           );
  
           //importing DOT_PRODUCT lib constructor(takes 1 arg of ptr to IOPERATION)
           dot_product_creator = boost::dll::import_alias(   // type of imported symbol must be explicitly specified
                   child_library_path,                                             // path to library
                   "create_dot_product",                                           // symbol to import
                   dll::load_mode::append_decorations                              // do append extensions and prefixes
           );
  
           //creating a ptr to SUM object
           boost::shared_ptr sum_ptr = sum_creator();
  
           //creating a ptr to DOT_PRODUCT object(passing above created SUM object ptr)
           boost::shared_ptr dot_product_ptr = dot_product_creator(sum_ptr);
           auto use_sum = true;
  
       const auto injector = di::make_injector(
             di::bind().to([&](const auto& injector) -> boost::shared_ptr {
               if (use_sum)
                 return injector.template create<boost::shared_ptr>();
               else
                 return injector.template create<boost::shared_ptr>();
           })
       );
  
       injector.create();
   }
  

• 文件application_main.cpp

   #include "boost/shared_ptr.hpp"
   #include <boost/dll/import.hpp>
   #include "boost/function.hpp"
   #include 
   #include "ioperation.hpp"
  
   namespace dll = boost::dll;
  
   int main(int argc, char* argv[]) {
  
       //setting up paths to library(.so) files
       boost::filesystem::path shared_library_path(argv[1]);    // argv[1] contains path to directory with our plugin library
           boost::filesystem::path child_library_path = shared_library_path/"dot_product";
       boost::filesystem::path parent_library_path = shared_library_path/"sum";
  
       //defining function types for lib constructors
       typedef boost::shared_ptr (sum_create_t)();
       typedef boost::shared_ptr (dot_product_create_t)(boost::shared_ptr);
       boost::function sum_creator;
       boost::function dot_product_creator;
  
       //importing SUM lib constructor(takes no arg)
       sum_creator = boost::dll::import_alias(   // type of imported symbol must be explicitly specified
               parent_library_path,                            // path to library
               "create_sum",                                   // symbol to import
               dll::load_mode::append_decorations              // do append extensions and prefixes
           );
  
       //importing DOT_PRODUCT lib constructor(takes 1 arg of ptr to IOPERATION)
       dot_product_creator = boost::dll::import_alias(   // type of imported symbol must be explicitly specified
               child_library_path,                                             // path to library
               "create_dot_product",                                           // symbol to import
               dll::load_mode::append_decorations                              // do append extensions and prefixes
           );
  
       //creating a ptr to PARENT_PLUGIN_SUM objecti
       boost::shared_ptr sum_ptr = sum_creator();
  
       //creating a ptr to CHILD_PLUGIN_MULT object(passing above created PARENT_PLUGIN_SUM object ptr)
       boost::shared_ptr dot_product_ptr = dot_product_creator(sum_ptr);
  
       //executing calculate methods for object ptrs
       std::cout << "Plugin Name: " << sum_ptr->name() << std::endl;
       std::cout << "sum_ptr->calculate(1, 2)[expected=3]: " << sum_ptr->calculate(1, 2) << std::endl;
       std::cout << "Plugin Name: " << dot_product_ptr->name() << std::endl;
           std::cout << "dot_product_ptr->calculate(1, 2)[expected=5]: " << dot_product_ptr->calculate(1, 2) << std::endl;
   }   
  

以下是观察到的准确误差：

    + echo '=> Compiling libraries and application_main.cpp ...'
    => Compiling libraries and application_main.cpp ...

    + g++ -std=c++14 -fPIC -c -o libsum.o sum.cpp
    + g++ -shared -o libsum.so libsum.o
    + g++ -std=c++14 -fPIC -c -o libdot_product.o dot_product.cpp
    + g++ -shared -o libdot_product.so libdot_product.o
    + g++ -std=c++14 -lboost_filesystem -lboost_system -ldl application_main.cpp -o application_main
    + echo '=> Compilation completed. '
    => Compilation completed. 

    + echo '=> Executing ./application_main .'
    => Executing ./application_main .

    + ./application_main .
    [sum_constructor]
    [dot_product_constructor]
    Plugin Name: sum
    sum_ptr->calculate(1, 2)[expected=3]: 3
    Plugin Name: dot_product
    dot_product_ptr->calculate(1, 2)[expected=5]: 5
    [~dot_product_destructor]
    [~sum_destructor]
    + echo ==================================
    ==================================
    + echo '=> Compiling application_di.cpp ...'

    => Compiling application_di.cpp …
    + g++ application_di.cpp -lboost_filesystem -lboost_system -ldl -o application_di
    application_di.cpp: In lambda function:
    application_di.cpp:62:65: error: type/value mismatch at argument 1 in template parameter list for ‘template class boost::shared_ptr’
        62 |               return injector.template create<boost::shared_ptr>();
            |                                                                 ^~~~~~~
    application_di.cpp:62:65: note:   expected a type, got ‘sum_ptr’
    application_di.cpp:64:65: error: type/value mismatch at argument 1 in template parameter list for ‘template class boost::shared_ptr’
        64 |               return injector.template create<boost::shared_ptr>();
            |                                                                 ^~~~~~~~~~~~~~~
    application_di.cpp:64:65: note:   expected a type, got ‘dot_product_ptr’