Re: [PR59319] output friends in debug info

[Alexandre Oliva <aoliva@redhat.com>]

On Mar 21, 2017, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Jan 27, 2017, Alexandre Oliva <aoliva@redhat.com> wrote:
>> On Oct 19, 2016, Alexandre Oliva <aoliva@redhat.com> wrote:
>>> On Sep 23, 2016, Alexandre Oliva <aoliva@redhat.com> wrote:
>>>> On Aug 30, 2016, Alexandre Oliva <aoliva@redhat.com> wrote:
>>>>> Handling non-template friends is kind of easy, [...]
>>>> Ping?
>>> Ping?  (conflicts resolved, patch refreshed and retested)
>> Ping?  (trivial conflicts resolved)
> Ping?  https://gcc.gnu.org/ml/gcc-patches/2017-01/msg02112.html
Ping?

>> 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.


>> for gcc/ChangeLog

>> PR debug/59319
>> * dwarf2out.c (class_types_with_friends): New.
>> (gen_friend_tags_for_type, gen_friend_tags): New.
>> (gen_member_die): Record class types with friends.
>> (deferred_marks): New.
>> (prune_unused_types_defer_undecided_mark_p): New.
>> (prune_unused_types_defer_mark): New.
>> (prune_unused_types_deferred_walk): New.
>> (prune_unused_types_walk): Defer DW_TAG_friend.
>> (prune_unused_types): Check deferred marks is empty on entry,
>> empty it after processing.
>> (dwarf2out_finish): Generate friend tags.
>> (dwarf2out_early_finish): Likewise.
>> * langhooks-def.h (LANG_HOOKS_GET_FRIENDS): New.
>> (LANG_HOOKS_FOR_TYPES_INITIALIZER): Add it.
>> * langhooks.h (lang_hooks_for_types): Add get_friends.
>> * hooks.c (hook_tree_const_tree_int_null): New.
>> * hooks.h (hook_tree_const_tree_int_null): Declare.

>> for gcc/cp/ChangeLog

>> PR debug/59319
>> * cp-objcp-common.c (cp_get_friends): New.
>> * cp-objcp-common.h (cp_get_friends): Declare.
>> (LANG_HOOKS_GET_FRIENDS): Override.
>> * cp-tree.h (enumerate_friend_specializations): Declare.
>> * pt.c (optimize_friend_specialization_lookup_p): New.
>> (retrieve_friend_specialization): New.
>> (enumerate_friend_specializations): New.
>> (register_specialization): Update DECL_TEMPLATE_INSTANTIATIONS
>> for functions, even after definition, if we are emitting debug
>> info.

>> for gcc/testsuite/ChangeLog

>> PR debug/59319
>> * g++.dg/debug/dwarf2/friend-1.C: New.
>> * g++.dg/debug/dwarf2/friend-2.C: New.
>> * g++.dg/debug/dwarf2/friend-3.C: New.
>> * g++.dg/debug/dwarf2/friend-4.C: New.
>> * g++.dg/debug/dwarf2/friend-5.C: New.
>> * g++.dg/debug/dwarf2/friend-6.C: New.
>> * g++.dg/debug/dwarf2/friend-7.C: New.
>> * g++.dg/debug/dwarf2/friend-8.C: New.
>> * g++.dg/debug/dwarf2/friend-9.C: New.
>> * g++.dg/debug/dwarf2/friend-10.C: New.
>> * g++.dg/debug/dwarf2/friend-11.C: New.
>> * g++.dg/debug/dwarf2/friend-12.C: New.
>> * g++.dg/debug/dwarf2/friend-13.C: New.
>> * g++.dg/debug/dwarf2/friend-14.C: New.
>> * g++.dg/debug/dwarf2/friend-15.C: New.
>> * g++.dg/debug/dwarf2/friend-16.C: New.
>> * g++.dg/debug/dwarf2/friend-17.C: New.
>> * g++.dg/debug/dwarf2/friend-18.C: New.

-- 
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