Re: [PATCH v18 23/26] c++: Implement __is_invocable built-in trait

[Ken Matsui <kmatsui@cs.washington.edu>]

On Thu, May 2, 2024 at 1:38 PM Jason Merrill <jason@redhat.com> wrote:
>
> On 5/2/24 16:12, Ken Matsui wrote:
> > This patch implements built-in trait for std::is_invocable.
> >
> > gcc/cp/ChangeLog:
> >
> >       * cp-trait.def: Define __is_invocable.
> >       * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_INVOCABLE.
> >       * semantics.cc (trait_expr_value): Likewise.
> >       (finish_trait_expr): Likewise.
> >       * cp-tree.h (build_invoke): New function.
> >       * method.cc (build_invoke): New function.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * g++.dg/ext/has-builtin-1.C: Test existence of __is_invocable.
> >       * g++.dg/ext/is_invocable1.C: New test.
> >       * g++.dg/ext/is_invocable2.C: New test.
> >       * g++.dg/ext/is_invocable3.C: New test.
> >       * g++.dg/ext/is_invocable4.C: New test.
> >
> > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > ---
> >   gcc/cp/constraint.cc                     |   6 +
> >   gcc/cp/cp-trait.def                      |   1 +
> >   gcc/cp/cp-tree.h                         |   2 +
> >   gcc/cp/method.cc                         | 134 +++++++++
> >   gcc/cp/semantics.cc                      |   5 +
> >   gcc/testsuite/g++.dg/ext/has-builtin-1.C |   3 +
> >   gcc/testsuite/g++.dg/ext/is_invocable1.C | 349 +++++++++++++++++++++++
> >   gcc/testsuite/g++.dg/ext/is_invocable2.C | 139 +++++++++
> >   gcc/testsuite/g++.dg/ext/is_invocable3.C |  51 ++++
> >   gcc/testsuite/g++.dg/ext/is_invocable4.C |  33 +++
> >   10 files changed, 723 insertions(+)
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable1.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable2.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable3.C
> >   create mode 100644 gcc/testsuite/g++.dg/ext/is_invocable4.C
> >
> > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> > index c28d7bf428e..6d14ef7dcc7 100644
> > --- a/gcc/cp/constraint.cc
> > +++ b/gcc/cp/constraint.cc
> > @@ -3792,6 +3792,12 @@ diagnose_trait_expr (tree expr, tree args)
> >       case CPTK_IS_FUNCTION:
> >         inform (loc, "  %qT is not a function", t1);
> >         break;
> > +    case CPTK_IS_INVOCABLE:
> > +      if (!t2)
> > +    inform (loc, "  %qT is not invocable", t1);
> > +      else
> > +    inform (loc, "  %qT is not invocable by %qE", t1, t2);
> > +      break;
> >       case CPTK_IS_LAYOUT_COMPATIBLE:
> >         inform (loc, "  %qT is not layout compatible with %qT", t1, t2);
> >         break;
> > diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> > index b1c875a6e7d..4e420d5390a 100644
> > --- a/gcc/cp/cp-trait.def
> > +++ b/gcc/cp/cp-trait.def
> > @@ -75,6 +75,7 @@ DEFTRAIT_EXPR (IS_EMPTY, "__is_empty", 1)
> >   DEFTRAIT_EXPR (IS_ENUM, "__is_enum", 1)
> >   DEFTRAIT_EXPR (IS_FINAL, "__is_final", 1)
> >   DEFTRAIT_EXPR (IS_FUNCTION, "__is_function", 1)
> > +DEFTRAIT_EXPR (IS_INVOCABLE, "__is_invocable", -1)
> >   DEFTRAIT_EXPR (IS_LAYOUT_COMPATIBLE, "__is_layout_compatible", 2)
> >   DEFTRAIT_EXPR (IS_LITERAL_TYPE, "__is_literal_type", 1)
> >   DEFTRAIT_EXPR (IS_MEMBER_FUNCTION_POINTER, "__is_member_function_pointer", 1)
> > diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> > index 1938ada0268..83dc20e1130 100644
> > --- a/gcc/cp/cp-tree.h
> > +++ b/gcc/cp/cp-tree.h
> > @@ -7338,6 +7338,8 @@ extern tree get_copy_assign                     (tree);
> >   extern tree get_default_ctor                        (tree);
> >   extern tree get_dtor                                (tree, tsubst_flags_t);
> >   extern tree build_stub_object                       (tree);
> > +extern tree build_invoke                     (tree, const_tree,
> > +                                              tsubst_flags_t);
> >   extern tree strip_inheriting_ctors          (tree);
> >   extern tree inherited_ctor_binfo            (tree);
> >   extern bool base_ctor_omit_inherited_parms  (tree);
> > diff --git a/gcc/cp/method.cc b/gcc/cp/method.cc
> > index 08a3d34fb01..faf932258e6 100644
> > --- a/gcc/cp/method.cc
> > +++ b/gcc/cp/method.cc
> > @@ -1928,6 +1928,140 @@ build_trait_object (tree type)
> >     return build_stub_object (type);
> >   }
> >
> > +/* [func.require] Build an expression of INVOKE(FN_TYPE, ARG_TYPES...).  If the
> > +   given is not invocable, returns error_mark_node.  */
> > +
> > +tree
> > +build_invoke (tree fn_type, const_tree arg_types, tsubst_flags_t complain)
> > +{
> > +  if (error_operand_p (fn_type) || error_operand_p (arg_types))
> > +    return error_mark_node;
> > +
> > +  gcc_assert (TYPE_P (fn_type));
> > +  gcc_assert (TREE_CODE (arg_types) == TREE_VEC);
> > +
> > +  /* Access check is required to determine if the given is invocable.  */
> > +  deferring_access_check_sentinel acs (dk_no_deferred);
> > +
> > +  /* INVOKE is an unevaluated context.  */
> > +  cp_unevaluated cp_uneval_guard;
> > +
> > +  bool is_ptrdatamem;
> > +  bool is_ptrmemfunc;
> > +  if (TREE_CODE (fn_type) == REFERENCE_TYPE)
> > +    {
> > +      tree deref_fn_type = TREE_TYPE (fn_type);
> > +      is_ptrdatamem = TYPE_PTRDATAMEM_P (deref_fn_type);
> > +      is_ptrmemfunc = TYPE_PTRMEMFUNC_P (deref_fn_type);
> > +
> > +      /* Dereference fn_type if it is a pointer to member.  */
> > +      if (is_ptrdatamem || is_ptrmemfunc)
> > +     fn_type = deref_fn_type;
> > +    }
> > +  else
> > +    {
> > +      is_ptrdatamem = TYPE_PTRDATAMEM_P (fn_type);
> > +      is_ptrmemfunc = TYPE_PTRMEMFUNC_P (fn_type);
> > +    }
> > +
> > +  if (is_ptrdatamem && TREE_VEC_LENGTH (arg_types) != 1)
> > +    {
> > +      if (complain & tf_error)
> > +     error ("pointer to data member type %qT can only be invoked with "
> > +            "one argument", fn_type);
> > +      return error_mark_node;
> > +    }
> > +
> > +  if (is_ptrmemfunc && TREE_VEC_LENGTH (arg_types) == 0)
> > +    {
> > +      if (complain & tf_error)
> > +     error ("pointer to member function type %qT must be invoked with "
> > +            "at least one argument", fn_type);
> > +      return error_mark_node;
> > +    }
> > +
> > +  /* Construct an expression of a pointer to member.  */
> > +  tree ptrmem_expr;
> > +  if (is_ptrdatamem || is_ptrmemfunc)
> > +    {
> > +      tree datum_type = TREE_VEC_ELT (arg_types, 0);
> > +
> > +      /* datum must be a class type or a reference/pointer to a class type.  */
> > +      if (!(CLASS_TYPE_P (datum_type)
> > +         || ((TYPE_REF_P (datum_type) || POINTER_TYPE_P (datum_type))
> > +             && CLASS_TYPE_P (TREE_TYPE (datum_type)))))
> > +     {
> > +       if (complain & tf_error)
> > +         error ("first argument type %qT of a pointer to member must be"
> > +                "a class type or a reference/pointer to a class type",
> > +                datum_type);
> > +       return error_mark_node;
> > +     }
> > +
> > +      bool is_refwrap = false;
> > +      if (CLASS_TYPE_P (datum_type))
> > +     {
> > +       /* 1.2 & 1.5: Handle std::reference_wrapper.  */
> > +       tree datum_decl = TYPE_NAME (TYPE_MAIN_VARIANT (datum_type));
> > +       if (decl_in_std_namespace_p (datum_decl))
> > +         {
> > +           const_tree name = DECL_NAME (datum_decl);
> > +           if (name && (id_equal (name, "reference_wrapper")))
> > +             {
> > +               /* Retrieve T from std::reference_wrapper<T>,
> > +                  i.e., decltype(datum.get()).  */
> > +               datum_type = TREE_VEC_ELT (TYPE_TI_ARGS (datum_type), 0);
> > +               is_refwrap = true;
> > +             }
> > +         }
> > +     }
> > +
> > +      tree ptrmem_class_type = TYPE_PTRMEM_CLASS_TYPE (fn_type);
> > +      const bool ptrmem_is_base_of_datum =
> > +     (NON_UNION_CLASS_TYPE_P (ptrmem_class_type)
> > +      && NON_UNION_CLASS_TYPE_P (datum_type)
>
> Why NON_UNION?  That doesn't seem to be based on anything in the standard.

This comes from the __is_base_of implementation in semantics.cc:

    case CPTK_IS_BASE_OF:
      return (NON_UNION_CLASS_TYPE_P (type1) && NON_UNION_CLASS_TYPE_P (type2)
      && (same_type_ignoring_top_level_qualifiers_p (type1, type2)
  || DERIVED_FROM_P (type1, type2)));

>
> This check and the one for reference_wrapper need to ignore
> REFERENCE_TYPE; INVOKE is defined in terms of expressions, and the type
> of an expression is never a reference.
>
> > +      && (same_type_ignoring_top_level_qualifiers_p (ptrmem_class_type,
> > +                                                     datum_type)
> > +          || DERIVED_FROM_P (ptrmem_class_type, datum_type)));
> > +
> > +      tree datum_expr = build_trait_object (datum_type);
> > +      if (!ptrmem_is_base_of_datum && !is_refwrap && !TYPE_REF_P (datum_type))
>
> ...so we shouldn't need to check TYPE_REF_P here.
>
> Jason
>
> > +     /* 1.3 & 1.6: Try to dereference datum_expr.  */
> > +     datum_expr = build_x_indirect_ref (UNKNOWN_LOCATION, datum_expr,
> > +                                        RO_UNARY_STAR, NULL_TREE, complain);
> > +      /* 1.1, 1.2, 1.4, & 1.5: Otherwise.  */
> > +
> > +      tree fn_expr = build_trait_object (fn_type);
> > +      ptrmem_expr = build_m_component_ref (datum_expr, fn_expr, complain);
> > +
> > +      if (error_operand_p (ptrmem_expr))
> > +     return error_mark_node;
> > +
> > +      if (is_ptrdatamem)
> > +     return ptrmem_expr;
> > +    }
> > +
> > +  /* Construct expressions for arguments to INVOKE.  For a pointer to member
> > +     function, the first argument, which is the object, is not arguments to
> > +     the function.  */
> > +  releasing_vec args;
> > +  for (int i = is_ptrmemfunc ? 1 : 0; i < TREE_VEC_LENGTH (arg_types); ++i)
> > +    {
> > +      tree arg_type = TREE_VEC_ELT (arg_types, i);
> > +      tree arg = build_trait_object (arg_type);
> > +      vec_safe_push (args, arg);
> > +    }
> > +
> > +  tree invoke_expr;
> > +  if (is_ptrmemfunc)
> > +    invoke_expr = build_offset_ref_call_from_tree (ptrmem_expr, &args,
> > +                                                complain);
> > +  else  /* 1.7.  */
> > +    invoke_expr = finish_call_expr (build_trait_object (fn_type), &args, false,
> > +                                 false, complain);
> > +  return invoke_expr;
> > +}
> > +
> >   /* Determine which function will be called when looking up NAME in TYPE,
> >      called with a single ARGTYPE argument, or no argument if ARGTYPE is
> >      null.  FLAGS and COMPLAIN are as for build_new_method_call.
>