Intercepting c++ exceptions

So my c++ program just crashed, and the error I got was:

terminate called after throwing an instance of 'std::length_error'
  what():  basi开发者_开发问答c_string::_S_create
Aborted

Now, what I've added recently to my code is a SIGSEGV handler, so if it was a segmentation fault, it would proceed to print the stack trace.

How do I go about making an exit handler for uncaught (or more like uncatchable) exceptions in c++?

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Use set_terminate function which sets the terminate handler function:

A terminate handler function is a function automatically called when the exception handling process has to be abandoned for some reason. This happens when a handler cannot be found for a thrown exception, or for some other exceptional circumstance that makes impossible to continue the handling process.

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Adding to the answer by @vitaut, if you are using C++11 you can check for and get the current exception within the handler specified by std::set_terminate.

According to Daniel Krügler who refers to the standard quoted below, there is an implicit exception handler active during the call to std::terminate, which means that we can use std::current_exception to both check whether there is an active exception and also examine it.

The C++11 standard working draft N3242, section 15.3.7 (emphasis mine):

A handler is considered active when initialization is complete for the formal parameter (if any) of the catch clause. [ Note: The stack will have been unwound at that point. — end note ] Also, an implicit handler is considered active when std::terminate() or std::unexpected() is entered due to a throw. A handler is no longer considered active when the catch clause exits or when std::unexpected() exits after being entered due to a throw.

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Stealing from Andrzej's C++ blog, here is an example of how this can be done:

[[noreturn]] void onTerminate() noexcept
{
    if( auto exc = std::current_exception() ) { 
        // we have an exception
        try{
            rethrow_exception( exc ); // throw to recognize the type
        }
        catch( MyException const& exc ) {
            // additional action
        }
        catch( MyOtherException const& exc ) {
            // additional action
        }
        catch( std::exception const& exc ) {
            // additional action
        }
        catch( ... ) {
            // additional action
        }
    }

    std::_Exit( EXIT_FAILURE );
}

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Just put try-catch(...) at the to level of your program. Something like this:

try {
   doStuff();
} catch( std::exception& e ) {
  //handle std::exception-derived exceptions
} catch(...) {
  //handle all other exceptions
}     

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You can install your own terminate handler with set_terminate.

You can catch all C++ exceptions with a catch-all clause catch (...) {}.