如何知道捕获了什么，同时捕获所有 C++ 异常

Question

One of the MFC function throwing an exception that cannot catch by std::exception or CException. So for identify the issue, I'm going to catch all exception as the last way (only to know what goes wrong, not for production).

try
{
  CPropertySheet::OnInitDialog();
}
catch (...)
{
  //need to know what did catch.
}

But is there a way to know what did catch after catching all the exception in C++? At-lease the error message of the exception or any other clue.

Answer 1

Short answer: no.

catch(...) catches everything without regards for the type of what was thrown. You could even throw an int and it would be caught. That also means you can't get an error message, because there might be none, like in the case of an int .

To solve your problem, you can only catch any exception type that might be thrown by the code in question, according to its documentation, but without the catch-all handler. If you still get an uncaught exception there might be some exceptions thrown by the runtime. You'll have to refer to your compiler's documentation to know which that may be. For example, in some runtimes an access violation (eg null ponter access) may be treated as exceptions that can be caught.

Another option would be to use a debugger and configure it to break when an exception is thrown. It can show you the exact location and the type of exception that is thrown. As you say it happens only in release build, you might try to use a release build with debug infos.

Answer 2

The ... is for a last resort.
But "most" exceptions in C++ are derived from std::exception or a class that is derived from this base class. Though it is not required "most" projects conform to this standard.

So you can achieve what you want by adding a catch for std::exception.

try
{
  CPropertySheet::OnInitDialog();
}
catch (std::exception const& e)
{
    std::cerr << "Exception: " << e.what() << "\n";
    throw;
}
catch (...)
{
    std::cerr << "Exception: >UNKNOWN<\n";
    throw;
}

Also some OS will also give you some help if the exception escapes main(). So rethrow the exception after generating an error message may help you track down the error.