Hi Ben, On Fri, 2025-11-07 at 08:09 -0800, Ben Woodard wrote: > On 11/7/25 6:58 AM, Mark Wielaard wrote: > > On Thu, 2025-11-06 at 11:34 -0800, Ben Woodard via Dwarf-discuss wrote: > > > > I think renaming is really confusing. And I think extending to > > supporting floating point types should be a separate issue that would > > also look at the other operators. > > > > Maybe a compromise would be to keep DW_OP_mod (and make DW_OP_rem an > > alias?) > > I would do it the other way around make DW_OP_mod be a legacy alias and > call the same operation DW_OP_rem.
I think that is fine, as long as they have the same constant value (0x1d). > With Jakub's example, I think that we have a compelling reason to expand > the domain of DW_OP_rem (the former DW_OP_mod) to include signed > integral types as well as unsigned integral types. His example seems to > require the semantics of C99's % operator (truncated division). > > If we do this, then it will be backward compatible. The only thing that > we would be changing is the domain over which the current DW_OP_mod > operates. We are not changing any of the semantics. Because the semantics weren't really defined for the expanded domain, which means e.g. gdb does interpret it differently. > I'm ambivalent about expanding the domain to floating point values. If > someone has a reason for having it work on floating point types, then > sure why not. It is a bit of extra code in every consumer but whatever. And it makes us have to define how floating point values are represented and pick a specific interpretation of the operations. > What I really care about is that when we update the description of > DW_OP_rem (the operation formerly known as DW_OP_mod) we specify both > the domain of the operator as well as the algorithm used. I think doing both a renaming and redefining the interpretation of the operation and domain at the same time is super confusing. Better to just introduce two new operations for the expanded domain. > > Then introduce new DW_OP_modulo (defined using floored > > division) > Again I'm personally ambivalent about the need for this. I don't think > that it is going to be used very often and I think if we do define it we > should consider pushing it into the new DW_OP_extended operation > encoding space. This will make its encoding a two byte operation but it > will reserve more of the one byte encodings for more frequently used > operations. Sure DW_OP_modulo and DW_OP_remainder could be "extended" operations. > > and DW_OP_remainder (defined using truncated division) > > operators that are only to be used with typed DWARF stack values? > > I really do believe that a better approach is to rename and expand the > domain of the current DW_OP_mod rather than adding another new special > purpose operator. I disagree. I think just leave DW_OP_mod for legacy operation on the generic type and have two clearly defined new DW_OP_modulo and DW_OP_remainder for typed DWARF stack values is much clearer. Cheers, Mark -- Dwarf-discuss mailing list [email protected] https://lists.dwarfstd.org/mailman/listinfo/dwarf-discuss
