On 27 Jun 2008, at 17:57, Nicola Pero wrote:
On 27 Jun 2008, at 16:35, Richard Frith-Macdonald wrote:
I was wondering if there was any good reason why gnustep-make
doesn't enable native exceptions by default if the compiler
supports it.
There are some overheads in enabling native exceptions.
I'm not too familiar with the issue, I only know that when I added
support
for native exceptions to gnustep-make and tried to make it the
default, someone
else came out and turned it off again by default claiming that the
overheads
are high.
That's fine btw - the main problem is that because you need a
special configure flag to turn them on,
nobody seems to be using native exceptions, so they don't get used /
tested / finished. :-(
Which is a pity, because they are a nice feature to have.
Apparently one problem is that they rely on unwinding the stack, and
if ffcall (and perhaps ffi) has been used to forward a method using an
invocation (including any distributed objects call) then the stack has
been messed up and the unwinding fails, so that the exception aborts
the process rather than being caught by a handler further down the
stack.
That's really bad news when using distributed objects ... you might
make a call to another application, an exception is raised in that
application, passed back and re-raised in your application which then
aborts your app!
So this would appear to be a rather severe drawback as invocations are
used quite extensively. Maybe the stack unwinding works if you used
libffi for your invocations, but libffi doesn't work on some platforms
(eg the debian 64bit intel box I develop on).
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