Re: [PATCH v2] c++: Don't quote nothrow in diagnostic

[Richard Biener <richard.guenther@gmail.com>]

On Mon, Sep 26, 2022 at 9:54 PM Marek Polacek <polacek@redhat.com> wrote:
>
> On Mon, Sep 26, 2022 at 12:34:04PM -0400, Jason Merrill wrote:
> > On 9/26/22 03:50, Richard Biener wrote:
> > > On Fri, Sep 23, 2022 at 8:41 PM Marek Polacek via Gcc-patches
> > > <gcc-patches@gcc.gnu.org> wrote:
> > > >
> > > > In <https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602057.html>
> > > > Jason noticed that we quote "nothrow" in diagnostics even though it's
> > > > not a keyword in C++.  Just removing the quotes didn't work because
> > > > then -Wformat-diag complains, so this patch replaces it with "no-throw".
> > > >
> > > > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > >
> > > That doesn't look like an improvement to me.  Can we quote 'nothrow()' instead?
>
> Understood.
>
> > nothrow() is a syntax error; the C++11 keyword is 'noexcept'. std::nothrow
> > is a dummy placement argument used to indicate that a new-expression should
> > return null rather than throw on failure.
> >
> > But bizarrely, the library traits use the word "nothrow".  Marek's patch
> > clarifies that we are not trying to refer to anything in the language.
> >
> > > I'd rather leave it alone than changing it to no-throw.  Why does -Wformat-diag
> > > complain?  If we shouldn't quote nothrow that should be adjusted?
> >
> > I think -Wformat-diag complains because "nothrow" is an attribute; it also
> > includes some other attribute names in the list of "keywords".
> >
> > I would also be fine with just removing the quotes and removing nothrow from
> > c_keywords.
>
> Like below?   Bootstrapped/regtested on x86_64-pc-linux-gnu.

Yes.  I assume that terms like "nothrow constructible" are used in the
C++ standard?

> Note that now I see warnings with my system compiler (gcc-12.2.1).  Can
> I commit the c-format.cc hunk to gcc 12 so that eventually even gcc 12
> stops warning?

Sure.

Thanks,
Richard.

> -- >8 --
> In <https://gcc.gnu.org/pipermail/gcc-patches/2022-September/602057.html>
> Jason noticed that we quote "nothrow" in diagnostics even though it's
> not a keyword in C++.  This patch removes the quotes and also drops
> "nothrow" from c_keywords.
>
> gcc/c-family/ChangeLog:
>
>         * c-format.cc (c_keywords): Drop nothrow.
>
> gcc/cp/ChangeLog:
>
>         * constraint.cc (diagnose_trait_expr): Say "nothrow" without quotes
>         rather than in quotes.
>
> gcc/testsuite/ChangeLog:
>
>         * g++.dg/cpp2a/concepts-traits3.C: Adjust expected diagnostics.
> ---
>  gcc/c-family/c-format.cc                      |  3 +--
>  gcc/cp/constraint.cc                          | 14 +++++++-------
>  gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C |  8 ++++----
>  3 files changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/gcc/c-family/c-format.cc b/gcc/c-family/c-format.cc
> index a6c380bf1c8..a2026591ed1 100644
> --- a/gcc/c-family/c-format.cc
> +++ b/gcc/c-family/c-format.cc
> @@ -2900,7 +2900,7 @@ static const token_t cxx_opers[] =
>    };
>
>  /* Common C/C++ keywords that are expected to be quoted within the format
> -   string.  Keywords like auto, inline, or volatile are exccluded because
> +   string.  Keywords like auto, inline, or volatile are excluded because
>     they are sometimes used in common terms like /auto variables/, /inline
>     function/, or /volatile access/ where they should not be quoted.  */
>
> @@ -2927,7 +2927,6 @@ static const token_t c_keywords[] =
>     NAME ("noinline", NULL),
>     NAME ("nonnull", NULL),
>     NAME ("noreturn", NULL),
> -   NAME ("nothrow", NULL),
>     NAME ("offsetof", NULL),
>     NAME ("readonly", "read-only"),
>     NAME ("readwrite", "read-write"),
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index 5839bfb4b52..266ec581a20 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -3592,13 +3592,13 @@ diagnose_trait_expr (tree expr, tree args)
>    switch (TRAIT_EXPR_KIND (expr))
>      {
>      case CPTK_HAS_NOTHROW_ASSIGN:
> -      inform (loc, "  %qT is not %<nothrow%> copy assignable", t1);
> +      inform (loc, "  %qT is not nothrow copy assignable", t1);
>        break;
>      case CPTK_HAS_NOTHROW_CONSTRUCTOR:
> -      inform (loc, "  %qT is not %<nothrow%> default constructible", t1);
> +      inform (loc, "  %qT is not nothrow default constructible", t1);
>        break;
>      case CPTK_HAS_NOTHROW_COPY:
> -      inform (loc, "  %qT is not %<nothrow%> copy constructible", t1);
> +      inform (loc, "  %qT is not nothrow copy constructible", t1);
>        break;
>      case CPTK_HAS_TRIVIAL_ASSIGN:
>        inform (loc, "  %qT is not trivially copy assignable", t1);
> @@ -3674,7 +3674,7 @@ diagnose_trait_expr (tree expr, tree args)
>        inform (loc, "  %qT is not trivially assignable from %qT", t1, t2);
>        break;
>      case CPTK_IS_NOTHROW_ASSIGNABLE:
> -      inform (loc, "  %qT is not %<nothrow%> assignable from %qT", t1, t2);
> +      inform (loc, "  %qT is not nothrow assignable from %qT", t1, t2);
>        break;
>      case CPTK_IS_CONSTRUCTIBLE:
>        if (!t2)
> @@ -3690,9 +3690,9 @@ diagnose_trait_expr (tree expr, tree args)
>        break;
>      case CPTK_IS_NOTHROW_CONSTRUCTIBLE:
>        if (!t2)
> -       inform (loc, "  %qT is not %<nothrow%> default constructible", t1);
> +       inform (loc, "  %qT is not nothrow default constructible", t1);
>        else
> -       inform (loc, "  %qT is not %<nothrow%> constructible from %qE", t1, t2);
> +       inform (loc, "  %qT is not nothrow constructible from %qE", t1, t2);
>        break;
>      case CPTK_HAS_UNIQUE_OBJ_REPRESENTATIONS:
>        inform (loc, "  %qT does not have unique object representations", t1);
> @@ -3701,7 +3701,7 @@ diagnose_trait_expr (tree expr, tree args)
>        inform (loc, "  %qT is not convertible from %qE", t2, t1);
>        break;
>      case CPTK_IS_NOTHROW_CONVERTIBLE:
> -       inform (loc, "  %qT is not %<nothrow%> convertible from %qE", t2, t1);
> +       inform (loc, "  %qT is not nothrow convertible from %qE", t2, t1);
>        break;
>      case CPTK_REF_CONSTRUCTS_FROM_TEMPORARY:
>        inform (loc, "  %qT is not a reference that binds to a temporary "
> diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
> index f20608b6918..3e87da4611e 100644
> --- a/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
> +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-traits3.C
> @@ -21,7 +21,7 @@ concept TriviallyAssignable = __is_trivially_assignable(T, U);
>
>  template<class T, class U>
>  concept NothrowAssignable = __is_nothrow_assignable(T, U);
> -// { dg-message "'S' is not 'nothrow' assignable from 'int'" "" { target *-*-* } .-1  }
> +// { dg-message "'S' is not nothrow assignable from 'int'" "" { target *-*-* } .-1  }
>
>  template<class T, class... Args>
>  concept Constructible = __is_constructible(T, Args...);
> @@ -37,9 +37,9 @@ concept TriviallyConstructible = __is_trivially_constructible(T, Args...);
>
>  template<class T, class... Args>
>  concept NothrowConstructible = __is_nothrow_constructible(T, Args...);
> -// { dg-message "'S' is not 'nothrow' default constructible" "" { target *-*-* } .-1  }
> -// { dg-message "'S' is not 'nothrow' constructible from 'int'" "" { target *-*-* } .-2  }
> -// { dg-message "'S' is not 'nothrow' constructible from 'int, char'" "" { target *-*-* } .-3  }
> +// { dg-message "'S' is not nothrow default constructible" "" { target *-*-* } .-1  }
> +// { dg-message "'S' is not nothrow constructible from 'int'" "" { target *-*-* } .-2  }
> +// { dg-message "'S' is not nothrow constructible from 'int, char'" "" { target *-*-* } .-3  }
>
>  template<class T>
>  concept UniqueObjReps = __has_unique_object_representations(T);
>
> base-commit: 7701ea4a70a5a5c0fd977da90a30ffc4f3f87617
> --
> 2.37.3
>