Re: C++ Exceptions Status

[Phil Muldoon <pmuldoon at redhat dot com>]

Ian Lance Taylor wrote:
> Phil Muldoon <pmuldoon@redhat.com> writes:
>
>   
> > The issue that I am currently wrestling with is how specific is this
> > unwind and exception work to C++? Are Java and Python exceptions
> > handled in the same way? And how can we avoid language specific
> > semantics in very general commands like "next"? Can we?
> >     
>
> The system you described is specific to systems that follow the
> Itanium C++ ABI (http://www.codesourcery.com/public/cxx-abi/).  gcc
> follows that ABI on most systems, not just Itanium systems.
>   

Yep totally, I should have pointed that out. Thanks for doing that, and 
posting the link.  I also found the unwinding description in this document:

http://www.x86-64.org/documentation/abi.pdf

very lucid too.

> On some systems gcc uses an exception handling system based on setjmp
> and longjmp.  This will be used if you configure gcc with
> --enable-sjlj-exceptions.  That is the default on HP/UX 10 and for
> older ARM targets.
>   

The existing "next" code should hopefully catch that via its existing 
longjmp/setjmp logic. But yeah, there is a lot of sjlj specifics defines 
throughout the code. Point well taken. Step two is to look at how C++ 
exceptions work here - when I can acquire a suitable target.

> When compiling with gcc to native code, Java exceptions are handled
> the same way as C++ exceptions.  When compiling to Java bytecode,
> exceptions are presumably handled within the JVM.  Most JVMs have
> various debugging hooks, but I don't know much about it.
>
> Python is not normally compiled to native code, and exceptions are
> handled within the Python interpreter.  I don't know much about that
> either.
>   

Did not know either of these facts, thanks for adding. My main concern 
is any solution that is proposed for C++ works in harmony with as many 
platforms and language exception handling methods as possible. Beyond 
that, I'm still investigating how to actual effect a change in "next" so 
it works with C++ exceptions ;)

Thanks,

Phil