Re: [LTO][PATCH] Fix long double precision problem

[Mark Mitchell <mark@codesourcery.com>]

Doug Kwan (關振德) wrote:
> The reason why I did the patch that way is to avoid changing the
> external debugging interface. If we need to serialize precisions, we
> may not need another GNU dwarf extension.  Currently already gcc emits
> DW_AT_bit_size and DW_AT_bit_offset pairs for integral types whose
> precisions are less than their bit width.  We can just add code to
> handling real scalar types.

Yes, I think you're 100% right.  I've reviewed the DWARF spec and,
indeed, DW_AT_bit_size/DW_AT_bit_offset are designed for exactly this
case.  So, we should just arrange to emit that information in dwarf2out.c.

> I am not sure what changes, if any, are required on the client side of
> the debugging information (e.g. gdb).  I am willing to implement those
> changes though.

I'm certainly not a GDB expert so I don't know what impact that might
have either.  It's just making the debug information more complete, so,
hopefully, it should Just Work, but it could of course also be the case
that something goes wrong.  Running the GDB testsuite is probably a good
first cut.  I'd suggest asking on the GDB mailing list.

Thanks,

-- 
Mark Mitchell
CodeSourcery
mark@codesourcery.com
(650) 331-3385 x713