[Dwarf-Discuss] Asm syntax for DWARF 5 line table info

[paul.robinson@sony.com]

cc binutils

> -----Original Message-----
> From: Nick Clifton [mailto:nickc at redhat.com]
> Sent: Friday, June 15, 2018 6:18 AM
> To: Robinson, Paul; dwarf-discuss at lists.dwarfstd.org
> Subject: Re: [Dwarf-Discuss] Asm syntax for DWARF 5 line table info
> 
> Hi Paul,
> 
> > I have been working on adding DWARF 5 support to LLVM, and some of
> > that support requires some assembler syntax tweaks.  It has been
> > suggested that I publicize those tweaks outside of the LLVM world,
> > and this list seems like the most likely place to find the people
> > who would be most interested in agreeing on a common syntax.
> 
> I think that it would also be wise to include the binutils project
> (binutils at sourceware.org) as they are responsible for the GNU
> Assembler (gas).
> 
> > I propose to add a new optional clause to the .file directive, like so:
> >
> >     .file filenumber [ "directory" ] "path" [ md5 checksum ]
> >
> > where md5 is a keyword and checksum is the integer checksum,
> > typically expressed as a hex 128-bit value.
> >
> > If all .file directives provide an md5 checksum, then the assembler
> > will put that checksum into the DWARF 5 file table.
> 
> If there are discrepancies in the md5 checksums, what should the assembler
> do ?

In LLVM, I have the assembler issue a warning if it sees inconsistent use
of the md5 clause.  It's not an error, because I do see it happen when
the compiler is reading a preprocessed file, and the assembler can't tell
the difference between something the compiler produced and a mistake made
by human coding.

Thanks,
--paulr

> 
> Cheers
>   Nick
> 
>