Re: What does a structured exception look like to C++?
On Fri, 21 Nov 2008 08:40:41 -0800, "rick cameron"
<rbc.sap@newsgroup.nospam> wrote:
That's a very interesting Q&A stream. Thanks for all the insight!
My code is a DLL that is used by a web server app. Each "job" processed by
the DLL runs on a separate thread, created by the calling app. I want to
make the DLL as robust as possible, so that even if there is an access
violation during the processing of a job, that condition is caught by the
DLL and just causes failure of that job, allowing other jobs to proceed.
(Such an AV probably represents a bug in the DLL - and I will obviously try
to fix it as soon as possible - but in the meanwhile robustness is good!)
To be truly robust in native code, I think you would need to launch
separate processes. The problem with threads is that they share address
space and all process state, so an AV (or other bug) in one may mean
trouble for others. I wouldn't totally hide the problem from the user, who
ought to be made aware that something went wrong, and his data may be at
risk. That may even be an issue for a thread terminated by a "normal" C++
exception.
I have done this by compiling with /EHa and putting a catch (...) clause in
the top-level API functions of the DLL. I suppose I could have used _try &
_catch instead, but for this specific use I don't see that there's a big
benefit in doing so - and the compiler doe not allow try/catch and
_try/_catch in the same function, so my code would be more complex!
Even if I were to use _try/_catch, and never use catch(...), I think I still
need to compile with /EHa, so that the objects on the stack are destroyed
when an AV happens, no?
Yes, if you want to use structured exceptions, you need to compile with
/EHa.
--
Doug Harrison
Visual C++ MVP