Re: Gnat, tasking, Vista

[Robert A Duff <bobduff@shell01.TheWorld.com>]

tmoran@acm.org writes:

>   A bug that is known and successfully worked-around isn't a bug, it's
> a feature.  Probably not a nice feature, but not a nasty surprise waiting
> to bite you.
>   Personally, I usually don't enjoy time spent finding the bugs in
> other people's (compilers or OSes etc) code.  I usually have little idea
> where the problem might be and there's a lot of grunt work trying to
> cut down to a small program that demonstrates the problem (see the
> recent thread on "Ada obfuscation").  And when there is a simple
> example, learning what to avoid may be its only payback, while those
> responsible take months, or even years, to release a corrected version.
>   My understanding is that the current Gnat is not a 3.15p with
> improvements, but is rather a substantially new thing, with new,
> unknown, bugs.  Is that a mis-understanding?

I can understand the reluctance to upgrade software, in general.
But if you're upgrading the OS (Windows XP to Vista) you really
need to upgrade GNAT as well.  There are several ways in which
Vista is incompatible, so it's not surprising that a version
of GNAT that predates Vista doesn't work!

The DEP issue was mentioned.  I suppose you can turn off DEP
in Vista, either in general, or for particular programs.
(I don't know -- I've never used Vista myself.)

The latest GNAT compiler no longer uses trampolines (which don't
work when DEP is turned on).  However, it can still generate code
that uses trampolines in some cases.  We've mostly fixed that, too,
but there's still a lot of testing to do.  Getting rid of
trampolines is a change in the guts of the back end, and
is target dependent.

Pointers to nested functions in C code will probably continue to use
trampolines for the forseeable future, but we can do better in pure
Ada code.

- Bob