Hi Mark, I looked at TotalView's DWARF reader, and omitting DW_AT_byte_size from DW_TAG_enumeration_type would require code changes. TotalView treats enums as self-contained types with a discrete byte length; in other words, enum types are not based on some other kind of type like "int" types. TotalView depends on the DW_AT_byte_size attribute to get the enum's byte length, and the DW_AT_encoding (if present) to determine the enum's signed-ness. It currently ignore any DW_AT_type attribute for enums.
Clearly, TotalView will need to change to accommodate DW_AT_type attributes in enum types, and I think we could also deal with a missing DW_AT_byte_size attribute *if* there is a DW_AT_type attribute that reference a valid type with a byte length. Cheers, John D. Mark Wielaard wrote: > Hi, > > I was adding the underlying type to an enumeration in a DWARF producer > (GCC) and wanted to drop the DW_AT_byte_size in case we have such an > underlying DW_AT_type. Since it looks redundant in that case. The > DW_AT_byte_size of the DW_TAG_enumeration should be equal to the size of > the underlying type if given. Or am I missing some subtle case were that > isn't/cannot be so? > > But the language of 5.7 Enumeration Type Entries isn't so clear that can > be done. Although it says "may have a DW_AT_type attribute", it does > imply that a DW_AT_byte_size must be given (by not saying "may"): "This > entry also has a DW_AT_byte_size attribute". > > Am I reading that too strictly? Or should I propose wording to make > clear that the DW_AT_byte_size is optional if a DW_AT_type has been > given (and only drop the redundant DW_AT_byte_size for DWARF5+ if such > wording is accepted)? > > I did check with at least one consumer (libabigail) that dropping the > DW_AT_byte_size would require some code updates, but they were not > opposed to just doing that. > > Thanks, > > Mark > > _______________________________________________ > Dwarf-Discuss mailing list > Dwarf-Discuss@lists.dwarfstd.org > http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org > _______________________________________________ Dwarf-Discuss mailing list Dwarf-Discuss@lists.dwarfstd.org http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org
