> If I used to compile a Ada- built system using PowerAda, and want to
change to
> GNAT, can there be problems? What sort of problems and can I do something
to
> prevent them? Its a very big system......

I experimented with porting a system comprising 20,000 files, millions of
SLOC,
from Apex Solaris to GNAT Solaris.  Took less than 80 hours to get
everything
to compile and link.  ALmost all of these changes were due to non-portable
Apex-specific features that had been used.  On several occasions, a
compiler
bug got in the way.  In all but one of these cases, the bug was fixed in a
new
compiler provided by FTP within  24 hours.  In that one case, we figured
out a way
to re-organize the code to avoid the bug.  GNAT support is considerably
more
expensive than the $10K Stephe guessed, but it's MUCH less than Apex.  At
least
that was the case way back then.

--
Wes Groleau
http://freepages.rootsweb.com/~wgroleau