Re: [PR59319] output friends in debug info

[Alexandre Oliva <aoliva at redhat dot com>]

On Aug 30, 2016, Alexandre Oliva <aoliva@redhat.com> wrote:

> Handling non-template friends is kind of easy, but it required a bit
> of infrastructure in dwarf2out to avoid (i) forcing debug info for
> unused types or functions: DW_TAG_friend DIEs are only emitted if
> their DW_AT_friend DIE is emitted, and (ii) creating DIEs for such
> types or functions just to have them discarded at the end.  To this
> end, I introduced a list (vec, actually) of types with friends,
> processed at the end of the translation unit, and a list of
> DW_TAG_friend DIEs that, when we're pruning unused types, reference
> DIEs that are still not known to be used, revisited after we finish
> deciding all other DIEs, so that we prune DIEs that would have
> referenced pruned types or functions.

> Handling template friends turned out to be trickier: there's no
> representation in DWARF for templates.  I decided to give debuggers as
> much information as possible, enumerating all specializations of
> friend templates and outputting DW_TAG_friend DIEs referencing them as
> well.  I considered marking those as DW_AT_artificial, to indicate
> they're not explicitly stated in the source code, but in the end we
> decided that was not useful.  The greatest challenge was to enumerate
> all specializations of a template.  It looked trivial at first, given
> DECL_TEMPLATE_INSTANTIATIONS, but it won't list specializations of
> class-scoped functions and of nested templates.  For other templates,
> I ended up writing code to look for specializations in the hashtables
> of decl or type specializations.  That's not exactly efficient, but it
> gets the job done.

Regstrapped on x86_64-linux-gnu and i686-linux-gnu, I'd failed to
mention.

Ping?

https://gcc.gnu.org/ml/gcc-patches/2016-08/msg02092.html

-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer