Re: debug/1621: Debugging with complex numbers

[Daniel Jacobowitz <drow@mvista.com>]

The following reply was made to PR debug/1621; it has been noted by GNATS.

From: Daniel Jacobowitz <drow@mvista.com>
To: Jim Wilson <wilson@redhat.com>
Cc: Wolfgang Bangerth <bangerth@ticam.utexas.edu>,
	"Joseph S. Myers" <jsm28@cam.ac.uk>, bangerth@dealii.org,
	gcc-bugs@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Subject: Re: debug/1621: Debugging with complex numbers
Date: Thu, 12 Dec 2002 14:51:56 -0500

 On Thu, Dec 12, 2002 at 10:55:17AM -0500, Jim Wilson wrote:
 > >I recommend emitting just the generic NF_COMPLEX and NF_FLOATING (?)
 > >for any of the unknown types.
 > 
 > NF_COMPLEX is supposed to be IEEE single complex.  There is no generic
 > value for complex types.  However, I do see your point, since we have the
 > type size anyways, we don't really need to distinguish between the different
 > complex types for IEEE FP targets.
 > 
 > There is a problem if we want to distinguish between IEEE and non-IEEE FP,
 > in which case the type size is not enough.  For instance, most RISC targets
 > use a 128-bit IEEE double-extended type.  However, some powerpc targets use
 > a 128-bit non-IEEE IBM pair-of-doubles type.  We can distinguish between these
 > two only if we have a special NF_* value for the IBM pair-of-doubles type.
 > Or alternatively, gdb just has to know that some targets use a non-IEEE long
 > double type.  This is different problem from the one we are trying to fix
 > though, and can be postponed for now.
 
 Right.  GDB already has a different mechanism to handle this case, so
 I'm not terribly worried about the details of using stabs and IEEE long
 double on a non-IEEE platform in this circumstance.
 
 > >First of all, for floating point types we could just continue to use
 > >'r'.  It's not problematic in that case.  On the other hand consistency
 > >is nice.
 > 
 > My patch continues to use 'r' for floating point types for now.  I didn't
 > want to break backwards compatibility for other stabs targets.  'R' will
 > presumably only work on the Sun debugger and gdb.  It is OK to use 'R' for
 > complex because it is an GNU C extension to ISO C90, so users can't expect
 > old debuggers to handle it correctly.
 
 Didn't you generate some 'R' entires for REAL_TYPE in the previous
 patch?
 
 > I will modify my patch to use NF_COMPLEX and NF_SINGLE as generic FP type
 > descriptors and add appropriate comments about what we are doing in order
 > to fix GCC PR debug/1621.
 
 Thank you!
 
 -- 
 Daniel Jacobowitz
 MontaVista Software                         Debian GNU/Linux Developer