On Wed, 2022-05-11 at 16:49 +0200, Martin Liška wrote:
> In case where we have 2 equally good candidates like
> -ftrivial-auto-var-init=
> -Wtrivial-auto-var-init
>
> for -ftrivial-auto-var-init, we should take the candidate that
> has a difference in trailing sign symbol.
>
> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>
> Ready to be installed?
> Thanks,
> Martin
>
> PR driver/105564
>
> gcc/ChangeLog:
>
> * spellcheck.cc (test_find_closest_string): Add new test.
> * spellcheck.h (class best_match): Prefer a difference in
> trailing sign symbol.
> ---
> gcc/spellcheck.cc | 9 +++++++++
> gcc/spellcheck.h | 17 ++++++++++++++---
> 2 files changed, 23 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/spellcheck.cc b/gcc/spellcheck.cc
> index 3e58344f510..f728573331f 100644
> --- a/gcc/spellcheck.cc
> +++ b/gcc/spellcheck.cc
> @@ -464,6 +464,15 @@ test_find_closest_string ()
> ASSERT_STREQ ("DWARF_GNAT_ENCODINGS_ALL",
> find_closest_string ("DWARF_GNAT_ENCODINGS_all",
> &candidates));
> +
> + /* Example from PR 105564 where option name with missing equal
> + sign should win. */
> + candidates.truncate (0);
> + candidates.safe_push ("-Wtrivial-auto-var-init");
> + candidates.safe_push ("-ftrivial-auto-var-init=");
> + ASSERT_STREQ ("-ftrivial-auto-var-init=",
> + find_closest_string ("-ftrivial-auto-var-init",
> + &candidates));
> }
>
> /* Test data for test_metric_conditions. */
> diff --git a/gcc/spellcheck.h b/gcc/spellcheck.h
> index 9b6223695be..9111ea08fc3 100644
> --- a/gcc/spellcheck.h
> +++ b/gcc/spellcheck.h
> @@ -128,11 +128,22 @@ class best_match
>
> /* Otherwise, compute the distance and see if the candidate
> has beaten the previous best value. */
> + const char *candidate_str = candidate_traits::get_string
> (candidate);
> edit_distance_t dist
> - = get_edit_distance (m_goal, m_goal_len,
> - candidate_traits::get_string (candidate),
> - candidate_len);
> + = get_edit_distance (m_goal, m_goal_len, candidate_str,
> candidate_len);
> +
> + bool is_better = false;
> if (dist < m_best_distance)
> + is_better = true;
> + else if (dist == m_best_distance)
> + {
> + /* Prefer a candidate has a difference in trailing sign
> character. */
> + if (candidate_str[candidate_len - 1] == '='
> + && m_goal[m_goal_len - 1] != '=')
> + is_better = true;
> + }
Thanks for working on this.
Maybe the comment should read:
/* Prefer a candidate that inserts a trailing '=',
so that for
"-ftrivial-auto-var-init"
we suggest
"-ftrivial-auto-var-init="
rather than
"-Wtrivial-auto-var-init". */
Is the logic correct? It's comparing the candidate with the goal,
rather than with the current best. What if both the candidate and the
current best both add a trailing equal sign?
I find the array access of the final character suspicious - is there
any chance that either of the lengths could be zero? I don't think so,
but maybe we should bulletproof things, and move the "is better"
comparison to a subroutine?
Hope this is constructive
Dave
> +
> + if (is_better)
> {
> m_best_distance = dist;
> m_best_candidate = candidate;
