Hi Paul, I too remember this discussion and clang's implementation is how I saw this being added when we did.
-eric On Mon, Feb 24, 2020 at 11:34 AM Robinson, Paul via Dwarf-Discuss < dwarf-discuss@lists.dwarfstd.org> wrote: > Hmmm. > > When the committee was reworking the file/dir tables for DWARF v5, > one thing that came up was that the root file/directory were *not* > in the .debug_line section, and therefore the line table could not > be interpreted fully without a .debug_info section, because that > was where the root file and compilation directory were kept--not > in the line table itself. Am I imagining this discussion? We > added text to the document specifically describing file/dir 0 and > that they were to be explicitly kept (duplicated from .debug_info) > so that the .debug_line section could be fully dumped even in the > absence of a corresponding .debug_info section. This was the > "strip all but the line table" scenario. > > I can easily believe that nobody *actually uses* file/dir 0, but > that's a different question from what producers are supposed to > produce in v5 and how consumers are supposed to interpret it. > > Offhand it looks like there are three possibilities: > a) Clang got it right and everyone else got it wrong. > b) The spec is ambiguous and we're observing the consequences. > c) Clang got it wrong and everyone else got it right. > > But in all three cases, we need to settle on (i) what the spec > actually says, (ii) does it say what the committee intended, > (iii) if not, what to do about it. > > I don't think we should start with (iii). > --paulr > > > -----Original Message----- > > From: Dwarf-Discuss <dwarf-discuss-boun...@lists.dwarfstd.org> On Behalf > > Of David Anderson via Dwarf-Discuss > > Sent: Friday, February 21, 2020 5:40 PM > > To: dwarf-discuss@lists.dwarfstd.org > > Subject: [Dwarf-Discuss] line table dir/file > > > > I've attached a pdf that > > shows some cases of current usage of the line > > table directory and file arrays and of indexes. > > > > clang seems (with my limited access to other compilers) > > the outlier in treating a index of 0 (from file [N] to > > the directory) as > > a 0 origin references. > > Only 0-origin for DWARF5. > > > > So reserving 0 as an index to the directories table > > to mean 'no directory available' would > > seem to be the right course. > > > > The standard (or an errata, if we do such a thing) > > needs works to establish 1-origin for these indexes into > > the directory table and clarifies the 1-origin > > indexes by referencing such in more places > > in the document. > > > > A tar.gz of the test setup is available by email > > if anyone cares. It is about 1 MiB in size (most > > of the size is in two ancient IRIX Elf files).. > > > > David Anderson > > > > _______________________________________________ > Dwarf-Discuss mailing list > Dwarf-Discuss@lists.dwarfstd.org > http://lists.dwarfstd.org/listinfo.cgi/dwarf-discuss-dwarfstd.org >
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