c++ - boost::exception 和 std::exception 之间的关系

Question

假设有如下代码:

try {
      // Do some boost stuff here
}
catch (const std::exception & stdEx) {
     cout << stdEx.what() << endl;
}

问题:

1) 我知道代码适用于某些 boost 异常，即使 std::exception 和 boost::exception 不在同一个继承路径上。为什么它会起作用？

2) 它是否适用于所有 boost 异常？换句话说，是否有可以触发低于 std::exception 处理程序的 boost::exception 处理程序的示例？

Answer 1

如您所说，boost::exception 不是从 std::exception 派生的。原因查看对应的FAQ :

Despite that virtual inheritance should be used in deriving from base exception types, quite often exception types (including the ones defined in the standard library) don't derive from std::exception virtually.

If boost::exception derives from std::exception, using the enable_error_info function with such user-defined types would introduce dangerous ambiguity which would break all catch(std::exception &) statements.

Of course, boost::exception should not be used to replace std::exception as a base type in exception type hierarchies. Instead, it should be included as a virtual base, in addition to std::exception (which should probably also be derived virtually.)

recommendation是让特定的 boost 异常类(实际上)从 boost::exception 和 std::exception 派生，而不仅仅是从 boost::exception.

一些 boost 库的异常仅来自 std::exception(如 boost::bad_lexical_cast )，有些来自两者(如 boost::xpressive::regex_error )。不过，我不知道仅从 boost::exception 派生的一个，所以我想说只捕获 std::exception 应该捕获所有。