Question

我最近开始使用boost :: exception。现在我想使用boost :: errinfo_nested_exception来打印有关错误原因的信息。问题是我无法弄清楚如何从原因中获取信息。我试过以下但没有成功：

#include <iostream>
#include <boost/exception/all.hpp>

struct myex : public virtual boost::exception {};

int main()
{
   myex cause;
   cause << boost::errinfo_file_name("causefile.cpp");

   try {
      myex ex;
      ex << boost::errinfo_nested_exception(boost::copy_exception(cause));
      throw ex;
   }
   catch (myex& e) {
      // Here I would like to extract file name from cause and print
      // it in a nice way, but I cant figure out what to do with a
      // boost::exception_ptr.
      const boost::exception_ptr* c = 
         boost::get_error_info<boost::errinfo_nested_exception>(e);

      // I cant do this:  
      // const std::string* file = boost::get_error_info<boost::errinfo_file_name>(*c);

      // Nor this: 
      // const std::string* file = boost::get_error_info<boost::errinfo_file_name>(**c);

      // This works fine and the nested exception is there, but that's not what I want.
      std::cout << boost::diagnostic_information(e) << std::endl;
   }

   return 0;
}

Answer 1

您需要重新抛出嵌套异常并检查：

const boost::exception_ptr* c = 
    boost::get_error_info<boost::errinfo_nested_exception>(e);
if(c) try {
    boost::rethrow_exception(*c);
} catch(boost::exception const& e) { // or a type derived from it
    const std::string* file = boost::get_error_info<boost::errinfo_file_name>(e);
    // ...
} catch(...) {
    // presumably you don't want the exception to escape if it is
    // not derived from boost::exception
}

我个人使用get_error_info包装器返回boost::get_error_info<some_error_info>(e)的结果，或者如果没有找到任何结果get_error_info<some_error_info>(nested)（这里是递归调用）或0那么没有嵌套异常（或者它不是error_info - 启用）。

或者/作为补充，您可以在函数中考虑上面的检查代码（不同的catch子句）：

std::string const* // or return a tuple of what you examined etc.
examine_exception()
{
    try {
        throw; // precondition: an exception is active
    } catch(boost::exception const& e) {
        // as above
        return ...;
    }
}

Answer 2

boost :: diagnostic_information是获取描述的正确方法。但你也可以为boost :: error_info（T）重载to_string： http://svn.boost.org/svn/boost/trunk/boost/exception/errinfo_errno.hpp

如何从boost :: errinfo_nested_exception中提取任何信息？

2 个答案: