Re: [PATCH v3 1/3] c++: sort candidates according to viability

[Jason Merrill <jason@redhat.com>]

On 10/27/23 15:55, Patrick Palka wrote:
> New in patch 1/3:
>    * consistently use "non-viable" instead of "unviable"
>      throughout
>    * make 'champ' and 'challenger' in 'tourney' be z_candidate**
>      to simplify moving 'champ' to the front of the list.  drive-by
>      cleanups in tourney, including renaming 'champ_compared_to_predecessor'
>      to 'previous_worse_champ' for clarity.
> New in patch 2/3:
>    * consistently use "non-viable" instead of "unviable" throughout
> New in patch 3/3:
>    * introduce new -fnote-all-cands flag that controls noting other
>      candidates when diagnosing deletedness, and also controls
>      noting "ignored" candidates in general.
> 
> -- >8 --
> 
> This patch:
> 
>    * changes splice_viable to move the non-viable candidates to the end
>      of the list instead of removing them outright
>    * makes tourney move the best candidate to the front of the candidate
>      list
>    * adjusts print_z_candidates to preserve our behavior of printing only
>      viable candidates when diagnosing ambiguity
>    * adds a parameter to print_z_candidates to control this default behavior
>      (the follow-up patch will want to print all candidates when diagnosing
>      deletedness)
> 
> Thus after this patch we have access to the entire candidate list through
> the best viable candidate.
> 
> This change also happens to fix diagnostics for the below testcase where
> we currently neglect to note the third candidate, since the presence of
> the two unordered non-strictly viable candidates causes splice_viable to
> prematurely get rid of the non-viable third candidate.
> 
> gcc/cp/ChangeLog:
> 
> 	* call.cc: Include "tristate.h".
> 	(splice_viable): Sort the candidate list according to viability.
> 	Don't remove non-viable candidates from the list.
> 	(print_z_candidates): Add defaulted only_viable_p parameter.
> 	By default only print non-viable candidates if there is no
> 	viable candidate.
> 	(tourney): Make 'candidates' parameter a reference.

Why, when all the callers use the return value?

OK without that change.

Jason