[Dwarf-Discuss] About self-referencial sized types

Jakub Jelinek jakub at redhat.com
Thu May 15 09:42:52 PDT 2014


On Thu, May 15, 2014 at 06:37:14PM +0200, Pierre-Marie de Rodat wrote:
> On 05/15/2014 04:30 PM, Jakub Jelinek wrote:
> >>Nothing: actually, the internal GCC representation for Ada arrays
> >>bounds (GENERIC trees) is already there and works well for quite a
> >>while. My problem here is that I do not know what DWARF operations
> >>to output in the DW_AT_{lower,upper}_bound attributes in order to
> >>retrieve array "neighbors" members so that we can compute the array
> >>bounds using them.
> >
> >If you are talking about GCC infrastructure here, look what Fortran uses
> >for it's VLAs, most likely this is just a matter of implementing
> >LANG_HOOKS_GET_ARRAY_DESCR_INFO for Ada for the cases where the bounds live
> >somewhere in some descriptor.
> 
> Yes, I've actually already started to work with this lang-hook so we
> can master the DWARF information output for Ada array types (very
> useful!). However, it does not solve the issue of knowing what DWARF
> operations to output in order to compute the bounds of VLAs
> *without* descriptors. (see the end of my 05/14/2014 mail)

You still build some trees in that langhook that describe the bounds etc.
and dwarf2out.c just transforms those trees into DWARF4 expression opcodes.

	Jakub



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