Re: [Caml-list] ANN: exn-source - exception backtraces with source code printing

[John Whitington <john@coherentgraphics.co.uk>]

Hi Gabriel,

Gabriel Scherer wrote:
>  > (we can't use exceptions at all inside a backtrace handler, for example)
>
> I'm a bit surprised by this. Part of the point of reifying traces into
> datatypes (raw_backtrace, backtrace_slot) was to make them persistent.
> set_uncaught_exception_handler is passed a raw trace that should not be
> mutated by raising new exceptions. What breaks if you use exceptions
> inside a backtrace handler?

To quote the documentation for set_uncaught_exception_handler: "If fn 
raises an exception, it is ignored."

This is a bit ambiguous -- it might mean

a) The uncaught exception handler you register won't get called from 
inside itself in the case of an uncaught exception. Nor will any such 
exceptions be handled by the standard exception handler; or

b) Exceptions in the handler literally have no effect.

I've done a little test just now, and it seems to be (a), so perhaps 
it's just in need of clarification in the documentation.

(It might be nice to have, for development, an option to have the 
default exception handler remain active, so it reports any exceptions 
escaping from the user-installed exception handler).

Thanks,

-- 
John Whitington
Director, Coherent Graphics Ltd
http://www.coherentpdf.com/