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FYI, for those of you not also on PLSIG (because we are the only embedded toolchain that implements Dwarf-2, I will be the secondary contact for it in the PPC-EABI):
- To: PLSIG <plsig@xopen.co.uk>
- Subject: Dwarf changes
- From: Michael Eager <eager@eagercon.com>
- Date: Mon, 06 Apr 1998 11:07:32 -0700
- Resent-Cc: recipient list not shown: ;
I attended the PowerPC Embedded ABI meeting last week. The PPC EABI committee, if you are not aware, is an ad hoc committee of companies supporting IBM/Motorola PowerPC. The PPC EABI endorses Dwarf 1.1 as its debugging format. Dwarf 1.1 is Dwarf 1 with some minor changes in the processor dependent areas. There have been other changes to Dwarf 1 proposed and apparently adopted by the PPC EABI committee, I believe to improve support for C++, but these have not been well publicized and I don't know the details. There was a long discussion about whether to extend Dwarf 1 or to endorse Dwarf 2. Some comments were raised that Dwarf 2 needs modifications, although with only a brief verbal presentation of the proposed changes I was not able to see a strong rationale for adopting them. I volunteered to "champion" changes to Dwarf 2 (with the assistance of Mike Meissner of Cygnus). Part of this discussion also revolved around changes to Dwarf 1. Some of the suggested changes were to pick out pieces of the Dwarf 2 specification and add them to Dwarf 1, and to add various other functionality to Dwarf 1 which is duplicated in Dwarf 2, but which would be implemented in a significantly different fashion. These extensions sounded like they would be incompatible with the current Dwarf 1 standard. As undercurrent for this discussion was the expressed opinion that since UI no longer exists and the PLSIG no longer has a sponsor, that the Dwarf spec has been abandoned and anyone can claim ownership. This is not the first time I have heard this opinion -- the last time was with the Tools Interface Standards committee, a Intel x86-oriented ad hoc industry group, which has since folded. I am concerned that a proliferation of different versions of Dwarf 1 or Dwarf 2 will make producing tools which use these formats more difficult, and that there will be no readily available and authoritative source of documentation which describes the format. We have to look no further than COFF (Common Object File Format) to find a format which is "common" but has several incompatible variations. The same holds true for IEEE 695, where the debug information has been changed significantly over the years, and Stabs, which have a number of variations, none of which seem well documented. I do believe that industry groups which are focused on a specific processor, whether it be PowerPC, x86, or other, should determine the processor dependent portions of the Dwarf specifications. I am far less sanguine about the appropriateness of such a narrow, processor oriented group deciding on structural changes in the specification. Is there interest in reconvening the PLSIG, looking for a sponsor, and asserting ownership/control over the Dwarf specification? -- Michael Eager eager@eagercon.com 1960 Park Blvd., Palo Alto, CA 94306 650-325-8077