Verbose Terminate Handler
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## Verbose Terminate Handler

If you are having difficulty with uncaught exceptions and want a little bit of help debugging the causes of the core dumps, you can make use of a GNU extension, the verbose terminate handler.

    #include <exception>

    int main()
    {
      std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
      ...

      throw anything;
    }

The `__verbose_terminate_handler` function obtains the name of the current exception, attempts to demangle it, and prints it to stderr. If the exception is derived from `exception` then the output from `what()` will be included.

Any replacement termination function is required to kill the program without returning; this one calls abort.

For example:

    #include <exception>
    #include <stdexcept>

    struct argument_error : public std::runtime_error
    {
      argument_error(const std::string& s): std::runtime_error(s) { }
    };

    int main(int argc)
    {
      std::set_terminate(__gnu_cxx::__verbose_terminate_handler);
      if (argc > 5)
        throw argument_error(“argc is greater than 5!”);
      else
        throw argc;
    }

With the verbose terminate handler active, this gives:

       % ./a.out
       terminate called after throwing a `int'
       Aborted
       % ./a.out f f f f f f f f f f f
       terminate called after throwing an instance of `argument_error'
       what(): argc is greater than 5!
       Aborted

The 'Aborted' line comes from the call to `abort()`, of course.

This is the default termination handler; nothing need be done to use it. To go back to the previous “silent death” method, simply include `exception` and `cstdlib`, and call

         std::set_terminate(std::abort);

After this, all calls to `terminate` will use `abort` as the terminate handler.

Note: the verbose terminate handler will attempt to write to stderr. If your application closes stderr or redirects it to an inappropriate location, `__verbose_terminate_handler` will behave in an unspecified manner.

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