On Fri, 27 Oct 2023, Patrick Palka wrote:
> On Fri, 27 Oct 2023, Jason Merrill wrote:
>
> > On 10/27/23 15:55, Patrick Palka wrote:
> > > With the previous two patches in place, we can now extend our
> > > deletedness diagnostic to note the other considered candidates, e.g.:
> > >
> > > deleted16.C: In function 'int main()':
> > > deleted16.C:10:4: error: use of deleted function 'void f(int)'
> > > 10 | f(0);
> > > | ~^~~
> > > deleted16.C:5:6: note: declared here
> > > 5 | void f(int) = delete;
> > > | ^
> > > deleted16.C:5:6: note: candidate: 'void f(int)' (deleted)
> > > deleted16.C:6:6: note: candidate: 'void f(...)'
> > > 6 | void f(...);
> > > | ^
> > > deleted16.C:7:6: note: candidate: 'void f(int, int)'
> > > 7 | void f(int, int);
> > > | ^
> > > deleted16.C:7:6: note: candidate expects 2 arguments, 1 provided
> > >
> > > These notes are controlled by a new command line flag -fnote-all-cands,
> > > which also controls whether we note ignored candidates more generally.
> > >
> > > gcc/ChangeLog:
> > >
> > > * doc/invoke.texi (C++ Dialect Options): Document -fnote-all-cands.
It just occurred to me that this despite this flag being C++ specific, it
probably should be documented under "Diagnostic Message Formatting Options",
like -fdiagnostics-show-template-tree is.
> > >
> > > gcc/c-family/ChangeLog:
> > >
> > > * c.opt: Add -fnote-all-cands.
> > >
> > > gcc/cp/ChangeLog:
> > >
> > > * call.cc (print_z_candidates): Only print ignored candidates
> > > when -fnote-all-cands is set.
> > > (build_over_call): When diagnosing deletedness, call
> > > print_z_candidates if -fnote-all-cands is set.
> >
> > My suggestion was also to suggest using the flag in cases where it would
> > make
> > a difference, e.g.
> >
> > note: some candidates omitted, use '-fnote-all-cands' to display them
>
> Ah thanks, fixed. That'll help a lot with discoverability of the flag.
>
> >
> > Maybe "-fdiagnostics-all-candidates"?
>
> Nice, that's a better name indeed :)
>
> How does the following look? Full bootstrap/regtest in progress.
>
> Here's the output of e.g. deleted16a.C. I think I'd prefer to not print
> the source line when emitting the suggestion, but I don't know how to do
> that properly (aside from e.g. emitting the note at UNKNOWN_LOCATION).
>
> In file included from gcc/testsuite/g++.dg/cpp0x/deleted16a.C:4:
> gcc/testsuite/g++.dg/cpp0x/deleted16.C: In function ‘int main()’:
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:21:4: error: use of deleted function
> ‘void f(int)’
> 21 | f(0); // { dg-error "deleted" }
> | ~^~~
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:6:6: note: declared here
> 6 | void f(int) = delete; // { dg-message "declared here" }
> | ^
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:21:4: note: use
> ‘-fdiagnostics-all-candidates’ to display considered candidates
> 21 | f(0); // { dg-error "deleted" }
> | ~^~~
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:22:4: error: use of deleted function
> ‘void g(int)’
> 22 | g(0); // { dg-error "deleted" }
> | ~^~~
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:12:6: note: declared here
> 12 | void g(int) = delete; // { dg-message "declared here" }
> | ^
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:22:4: note: use
> ‘-fdiagnostics-all-candidates’ to display considered candidates
> 22 | g(0); // { dg-error "deleted" }
> | ~^~~
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:23:4: error: use of deleted function
> ‘void h(T, T) [with T = int]’
> 23 | h(1, 1); // { dg-error "deleted" }
> | ~^~~~~~
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:17:24: note: declared here
> 17 | template<class T> void h(T, T) = delete; // { dg-message "declared
> here|candidate" }
> | ^
> gcc/testsuite/g++.dg/cpp0x/deleted16.C:23:4: note: use
> ‘-fdiagnostics-all-candidates’ to display considered candidates
> 23 | h(1, 1); // { dg-error "deleted" }
> | ~^~~~~~
>
> -- >8 --
>
>
> Subject: [PATCH 3/3] c++: note other candidates when diagnosing deletedness
>
> With the previous two patches in place, we can now extend our
> deletedness diagnostic to note the other considered candidates, e.g.:
>
> deleted16.C: In function 'int main()':
> deleted16.C:10:4: error: use of deleted function 'void f(int)'
> 10 | f(0);
> | ~^~~
> deleted16.C:5:6: note: declared here
> 5 | void f(int) = delete;
> | ^
> deleted16.C:5:6: note: candidate: 'void f(int)' (deleted)
> deleted16.C:6:6: note: candidate: 'void f(...)'
> 6 | void f(...);
> | ^
> deleted16.C:7:6: note: candidate: 'void f(int, int)'
> 7 | void f(int, int);
> | ^
> deleted16.C:7:6: note: candidate expects 2 arguments, 1 provided
>
> These notes are controlled by a new command line flag
> -fdiagnostics-all-candidates which also controls whether we note
> ignored candidates more generally.
>
> gcc/ChangeLog:
>
> * doc/invoke.texi (C++ Dialect Options): Document
> -fdiagnostics-all-candidates.
>
> gcc/c-family/ChangeLog:
>
> * c.opt: Add -fdiagnostics-all-candidates.
>
> gcc/cp/ChangeLog:
>
> * call.cc (print_z_candidates): Only print ignored candidates
> when -fdiagnostics-all-candidates is set, otherwise suggest
> the flag.
> (build_over_call): When diagnosing deletedness, note
> other candidates only if -fdiagnostics-all-candidates is
> set, otherwise suggest the flag.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/overload/error6.C: Pass -fdiagnostics-all-candidates.
> * g++.dg/cpp0x/deleted16.C: New test.
> * g++.dg/cpp0x/deleted16a.C: New test.
> * g++.dg/overload/error6a.C: New test.
> ---
> gcc/c-family/c.opt | 4 ++++
> gcc/cp/call.cc | 19 ++++++++++++++++++-
> gcc/doc/invoke.texi | 5 +++++
> gcc/testsuite/g++.dg/cpp0x/deleted16.C | 25 +++++++++++++++++++++++++
> gcc/testsuite/g++.dg/cpp0x/deleted16a.C | 12 ++++++++++++
> gcc/testsuite/g++.dg/overload/error6.C | 1 +
> gcc/testsuite/g++.dg/overload/error6a.C | 6 ++++++
> 7 files changed, 71 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/deleted16.C
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/deleted16a.C
> create mode 100644 gcc/testsuite/g++.dg/overload/error6a.C
>
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index 44b9c862c14..c12c86bb8ed 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -1781,6 +1781,10 @@ fdiagnostics-show-template-tree
> C++ ObjC++ Var(flag_diagnostics_show_template_tree) Init(0)
> Print hierarchical comparisons when template types are mismatched.
>
> +fdiagnostics-all-candidates
> +C++ ObjC++ Var(flag_diagnostics_all_candidates)
> +Note all candidates during overload resolution failure.
> +
> fdirectives-only
> C ObjC C++ ObjC++
> Preprocess directives only.
> diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
> index 81cc029dddb..e9c099eedb8 100644
> --- a/gcc/cp/call.cc
> +++ b/gcc/cp/call.cc
> @@ -4090,6 +4090,12 @@ print_z_candidates (location_t loc, struct z_candidate
> *candidates,
> {
> if (only_viable_p.is_true () && candidates->viable != 1)
> break;
> + if (ignored_candidate_p (candidates) &&
> !flag_diagnostics_all_candidates)
> + {
> + inform (loc, "some candidates omitted; "
> + "use %<-fdiagnostics-all-candidates%> to display them");
> + break;
> + }
> print_z_candidate (loc, N_("candidate:"), candidates);
> }
> }
> @@ -9933,7 +9939,18 @@ build_over_call (struct z_candidate *cand, int flags,
> tsubst_flags_t complain)
> if (DECL_DELETED_FN (fn))
> {
> if (complain & tf_error)
> - mark_used (fn);
> + {
> + mark_used (fn);
> + if (cand->next)
> + {
> + if (flag_diagnostics_all_candidates)
> + print_z_candidates (input_location, cand,
> /*only_viable_p=*/false);
> + else
> + inform (input_location,
> + "use %<-fdiagnostics-all-candidates%> to display "
> + "considered candidates");
> + }
> + }
> return error_mark_node;
> }
>
> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> index 5a9284d635c..7e9f68d31b3 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -3311,6 +3311,11 @@ called. If the handler returns, execution continues
> normally.
> @item -fcoroutines
> Enable support for the C++ coroutines extension (experimental).
>
> +@opindex fdiagnostics-all-candidates
> +@item -fdiagnostics-all-candidates
> +Permit the C++ front end to note all candidates during overload resolution
> +failure, including when a deleted function is selected.
> +
> @opindex fno-elide-constructors
> @opindex felide-constructors
> @item -fno-elide-constructors
> diff --git a/gcc/testsuite/g++.dg/cpp0x/deleted16.C
> b/gcc/testsuite/g++.dg/cpp0x/deleted16.C
> new file mode 100644
> index 00000000000..d4347942c42
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/deleted16.C
> @@ -0,0 +1,25 @@
> +// Verify -fdiagnostics-all-candidates makes us note other candidates
> +// when a deleted function is selected by overload resolution.
> +// { dg-do compile { target c++11 } }
> +// { dg-additional-options "-fdiagnostics-all-candidates" }
> +
> +void f(int) = delete; // { dg-message "declared here" }
> +void f(...); // { dg-message "candidate" }
> +void f(int, int); // { dg-message "candidate" }
> +
> +// An example where the perfect candidate optimization causes us
> +// to ignore function templates.
> +void g(int) = delete; // { dg-message "declared here" }
> +template<class T> void g(T); // { dg-message "candidate" }
> +
> +// An example where we have a strictly viable candidate and
> +// an incompletely considered bad candidate.
> +template<class T> void h(T, T) = delete; // { dg-message "declared
> here|candidate" }
> +void h(int*, int) = delete; // { dg-message "candidate" }
> +
> +int main() {
> + f(0); // { dg-error "deleted" }
> + g(0); // { dg-error "deleted" }
> + h(1, 1); // { dg-error "deleted" }
> + // { dg-error "invalid conversion" "" { target *-*-* } .-1 } when
> noting 2nd cand
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp0x/deleted16a.C
> b/gcc/testsuite/g++.dg/cpp0x/deleted16a.C
> new file mode 100644
> index 00000000000..e62306fa3d1
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/deleted16a.C
> @@ -0,0 +1,12 @@
> +// Verify we suggest -fdiagnostics-all-candidates when diagnosing
> +// overload resolution selecting a deleted function.
> +// { dg-do compile { target c++11 } }
> +#include "deleted16.C"
> +
> +// { dg-error "deleted" "" { target *-*-* } 21 }
> +// { dg-error "deleted" "" { target *-*-* } 22 }
> +// { dg-error "deleted" "" { target *-*-* } 23 }
> +
> +// { dg-message "use '-fdiagnostics-all-candidates'" "" { target *-*-* } 21 }
> +// { dg-message "use '-fdiagnostics-all-candidates'" "" { target *-*-* } 22 }
> +// { dg-message "use '-fdiagnostics-all-candidates'" "" { target *-*-* } 23 }
> diff --git a/gcc/testsuite/g++.dg/overload/error6.C
> b/gcc/testsuite/g++.dg/overload/error6.C
> index 86a12eaa8de..3186a297bfc 100644
> --- a/gcc/testsuite/g++.dg/overload/error6.C
> +++ b/gcc/testsuite/g++.dg/overload/error6.C
> @@ -1,5 +1,6 @@
> // Verify we note even non-template candidates when diagnosing
> // overload resolution failure for a template-id.
> +// { dg-additional-options "-fdiagnostics-all-candidates" }
>
> template<class T> void f(T); // { dg-message "candidate" }
> void f(int); // { dg-message {candidate: 'void f\(int\)' \(ignored\)} }
> diff --git a/gcc/testsuite/g++.dg/overload/error6a.C
> b/gcc/testsuite/g++.dg/overload/error6a.C
> new file mode 100644
> index 00000000000..e86ab5158ab
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/overload/error6a.C
> @@ -0,0 +1,6 @@
> +// Verify we suggest -fdiagnostics-all-candidates when there are
> +// omitted candidates.
> +#include "error6.C"
> +
> +// { dg-error "no match" "" { target *-*-* } 9 }
> +// { dg-message "use '-fdiagnostics-all-candidates'" "" { target *-*-* } 9 }
> --
> 2.42.0.482.g2e8e77cbac
>
