Re: [PATCH v2 1/4] c++: Implement __add_pointer built-in trait

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

On Wed, Feb 14, 2024 at 12:19 PM Patrick Palka <ppalka@redhat.com> wrote:
>
> On Wed, 14 Feb 2024, Ken Matsui wrote:
>
> > This patch implements built-in trait for std::add_pointer.
> >
> > gcc/cp/ChangeLog:
> >
> >       * cp-trait.def: Define __add_pointer.
> >       * semantics.cc (finish_trait_type): Handle CPTK_ADD_POINTER.
> >
> > gcc/testsuite/ChangeLog:
> >
> >       * g++.dg/ext/has-builtin-1.C: Test existence of __add_pointer.
> >       * g++.dg/ext/add_pointer.C: New test.
> >
> > Signed-off-by: Ken Matsui <kmatsui@gcc.gnu.org>
> > ---
> >  gcc/cp/cp-trait.def                      |  1 +
> >  gcc/cp/semantics.cc                      |  9 ++++++
> >  gcc/testsuite/g++.dg/ext/add_pointer.C   | 37 ++++++++++++++++++++++++
> >  gcc/testsuite/g++.dg/ext/has-builtin-1.C |  3 ++
> >  4 files changed, 50 insertions(+)
> >  create mode 100644 gcc/testsuite/g++.dg/ext/add_pointer.C
> >
> > diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def
> > index 394f006f20f..cec385ee501 100644
> > --- a/gcc/cp/cp-trait.def
> > +++ b/gcc/cp/cp-trait.def
> > @@ -48,6 +48,7 @@
> >  #define DEFTRAIT_TYPE_DEFAULTED
> >  #endif
> >
> > +DEFTRAIT_TYPE (ADD_POINTER, "__add_pointer", 1)
> >  DEFTRAIT_EXPR (HAS_NOTHROW_ASSIGN, "__has_nothrow_assign", 1)
> >  DEFTRAIT_EXPR (HAS_NOTHROW_CONSTRUCTOR, "__has_nothrow_constructor", 1)
> >  DEFTRAIT_EXPR (HAS_NOTHROW_COPY, "__has_nothrow_copy", 1)
> > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> > index 57840176863..e23693ab57f 100644
> > --- a/gcc/cp/semantics.cc
> > +++ b/gcc/cp/semantics.cc
> > @@ -12760,6 +12760,15 @@ finish_trait_type (cp_trait_kind kind, tree type1, tree type2,
> >
> >    switch (kind)
> >      {
> > +    case CPTK_ADD_POINTER:
> > +      if (TREE_CODE (type1) == FUNCTION_TYPE
> > +       && ((TYPE_QUALS (type1) & (TYPE_QUAL_CONST | TYPE_QUAL_VOLATILE))
> > +            || FUNCTION_REF_QUALIFIED (type1)))
>
> In other parts of the front end, e.g. the POINTER_TYPE case of tsubst, in
> build_trait_object, grokdeclarator and get_typeid, it seems we check for
> an unqualified function type with
>
>   (type_memfn_quals (type) != TYPE_UNQUALIFIED
>    && type_mem_rqual (type) != REF_QUAL_NONE)
>
> which should be equivalent to your formulation except it also checks
> for non-standard qualifiers such as __restrict.
>
> I'm not sure what a __restrict-qualified function type means or if we
> care about the semantics of __add_pointer(void () __restrict), but I
> reckon we might as well be consistent and use the type_mem_quals/rqual
> formulation in new code too?
>

I see and agree.  Thank you for your review!  I will update this patch.

> > +     return type1;
> > +      if (TYPE_REF_P (type1))
> > +     type1 = TREE_TYPE (type1);
> > +      return build_pointer_type (type1);
> > +
> >      case CPTK_REMOVE_CV:
> >        return cv_unqualified (type1);
> >
> > diff --git a/gcc/testsuite/g++.dg/ext/add_pointer.C b/gcc/testsuite/g++.dg/ext/add_pointer.C
> > new file mode 100644
> > index 00000000000..3091510f3b5
> > --- /dev/null
> > +++ b/gcc/testsuite/g++.dg/ext/add_pointer.C
> > @@ -0,0 +1,37 @@
> > +// { dg-do compile { target c++11 } }
> > +
> > +#define SA(X) static_assert((X),#X)
> > +
> > +class ClassType { };
> > +
> > +SA(__is_same(__add_pointer(int), int*));
> > +SA(__is_same(__add_pointer(int*), int**));
> > +SA(__is_same(__add_pointer(const int), const int*));
> > +SA(__is_same(__add_pointer(int&), int*));
> > +SA(__is_same(__add_pointer(ClassType*), ClassType**));
> > +SA(__is_same(__add_pointer(ClassType), ClassType*));
> > +SA(__is_same(__add_pointer(void), void*));
> > +SA(__is_same(__add_pointer(const void), const void*));
> > +SA(__is_same(__add_pointer(volatile void), volatile void*));
> > +SA(__is_same(__add_pointer(const volatile void), const volatile void*));
> > +
> > +void f1();
> > +using f1_type = decltype(f1);
> > +using pf1_type = decltype(&f1);
> > +SA(__is_same(__add_pointer(f1_type), pf1_type));
> > +
> > +void f2() noexcept; // PR libstdc++/78361
> > +using f2_type = decltype(f2);
> > +using pf2_type = decltype(&f2);
> > +SA(__is_same(__add_pointer(f2_type), pf2_type));
> > +
> > +using fn_type = void();
> > +using pfn_type = void(*)();
> > +SA(__is_same(__add_pointer(fn_type), pfn_type));
> > +
> > +SA(__is_same(__add_pointer(void() &), void() &));
> > +SA(__is_same(__add_pointer(void() & noexcept), void() & noexcept));
> > +SA(__is_same(__add_pointer(void() const), void() const));
> > +SA(__is_same(__add_pointer(void(...) &), void(...) &));
> > +SA(__is_same(__add_pointer(void(...) & noexcept), void(...) & noexcept));
> > +SA(__is_same(__add_pointer(void(...) const), void(...) const));
> > diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> > index 02b4b4d745d..56e8db7ac32 100644
> > --- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> > +++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C
> > @@ -2,6 +2,9 @@
> >  // { dg-do compile }
> >  // Verify that __has_builtin gives the correct answer for C++ built-ins.
> >
> > +#if !__has_builtin (__add_pointer)
> > +# error "__has_builtin (__add_pointer) failed"
> > +#endif
> >  #if !__has_builtin (__builtin_addressof)
> >  # error "__has_builtin (__builtin_addressof) failed"
> >  #endif
> > --
> > 2.43.0
> >
> >
>