On Tue, 2014-04-01 at 18:42 -0700, Michael Eager wrote: > On 04/01/14 13:54, Mark Wielaard wrote: > > > What about using the presence of a DW_AT_external attribute on the data > > object that has a single location expression to know whether the described > > location is valid/visible outside of the enclosing lexical scope? > > > > Using that or some new flag (DW_AT_global_scope) to mark a data object > > that has a single location description with global scope might be cheaper > > than encoding it with a location list pointer and a default entry. > > Both DW_AT_external attribute and a hypothetical DW_AT_global_scope > attribute would describe scope, not the storage life of the object. > C unfortunately has confabulated the two concepts.
In practice I believe DW_AT_external does both and I have used it that way to know whether to trust a single location description is globally valid. But yes, just like lifetime both "external" and "scope" are again bad words to use in this case and don't really express the thing we want (they might only accidentally). What about we call the flag attribute DW_AT_global_visible or DW_AT_global_location then it would be clear I think because it signals this isn't about language or DWARF tree (lexical) scoping? > Objects which have only a single location can be described with a location > expression. They don't need a location list with a default entry. For a data object that has a single location descriptor (DW_AT_location in exprloc class form), the valid range is given by the address ranges of the DIEs that own the data object. So it only lets me express the location in a restricted range. I do need to use a location list with (just) a default entry if I want to indicate that the location description has a valid global range. Is the above correct? Or is there another way to express that a location description is globally valid? Or am I misunderstanding the purpose of having a default entry in a location list? Thanks, Mark _______________________________________________ Dwarf-Discuss mailing list Dwarf-Discuss@lists.dwarfstd.org http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org
