Catching a hot potato

[Walter Bright]

On 10/15/2011 3:29 AM, Gor Gyolchanyan wrote:
> The other day i was re-reading the std.exception docs and stumbled
> upon "It's ill-advised to catch anything, that is not Exception or
> derived from it".
> Can you show me examples when catching a Throwable is a good idea?

When there's something your program needs to do in order to shut down 
gracefully (such as "engage the backup", or "try to save the user's 
data"), or if you want to generate a log message before stopping the 
program.

Catching it can also be used to shut down a failing subsystem and 
restart it.

> Also, i had some thoughts about catching AcessViolation exception in a
> modular application to avoid my app crashing when a module crashes,
> but i was told, that segfaults indicate a messed up memory and nothing
> is guaranteed to work after a segfault.

That's true, an access violation means you've got likely got memory 
corruption somewhere.

> My question is, is it true, that segfault means THE END, and if so,
> what's the point in allowing to catch it?

Debuggers need to catch all seg faults from the debuggee. OS services 
need to catch page faults in order to implement demand paged virtual 
memory, stack faults in order to extend the stack segment, etc.

> Also, how do i prevent DLLs from crashing my process like that?

You'll need to figure out how to run your DLL in a separate address 
space, like a debugger would.