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[69.118.112.187]) by smtp.gmail.com with ESMTPSA id bq26-20020a05622a1c1a00b003f9c2f51558sm1245132qtb.24.2023.06.20.09.00.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Jun 2023 09:00:59 -0700 (PDT) From: Patrick Palka X-Google-Original-From: Patrick Palka Date: Tue, 20 Jun 2023 12:00:59 -0400 (EDT) To: Ken Matsui cc: gcc-patches@gcc.gnu.org, libstdc++@gcc.gnu.org Subject: Re: [PATCH v7 5/6] c++, libstdc++: implement __is_void built-in trait In-Reply-To: <20230612224909.21188-6-kmatsui@cs.washington.edu> Message-ID: <5921351a-1a1f-a4ba-7074-2a57b8854d4a@idea> References: <20230612224109.20749-1-kmatsui@cs.washington.edu> <20230612224909.21188-1-kmatsui@cs.washington.edu> <20230612224909.21188-6-kmatsui@cs.washington.edu> MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII X-Spam-Status: No, score=-13.8 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On Mon, 12 Jun 2023, Ken Matsui via Libstdc++ wrote: > This patch implements built-in trait for std::is_void. Since the new built-in > name is __is_void, to avoid unintentional macro replacement, this patch also > involves the removal of the existing __is_void in helper_functions.h and > cpp_type_traits.h and renaming __is_void to ____is_void in the test file, > pr46567.C. Hmm, I suspect an __is_void built-in won't show an improvement over the current is_void implementation in terms of four explicit specializations. And given the __is_void name conflict in cpp_type_traits.h (which means GCC trunk will reject older libstdc++ headers at least until we get smarter about how we recognize built-ins), I'm leaning towards not implementing an __is_void built-in for now. In that case we should probably define a built-in for is_object since we can no longer implement it solely in terms of other built-ins, and fortunately the name __is_object seems to never have been used in libstdc++ so we won't have to deal with any name conflicts unlike with __is_void. Jonathan, what do you think? > > gcc/cp/ChangeLog: > > * cp-trait.def: Define __is_void. > * constraint.cc (diagnose_trait_expr): Handle CPTK_IS_VOID. > * semantics.cc (trait_expr_value): Likewise. > (finish_trait_expr): Likewise. > > gcc/testsuite/ChangeLog: > > * g++.dg/tm/pr46567.C (__is_void): Rename to ... > (____is_void): ... this. > * g++.dg/ext/has-builtin-1.C: Test existence of __is_void. > * g++.dg/ext/is_void.C: New test. > > libstdc++-v3/ChangeLog: > > * include/debug/helper_functions.h (_DiffTraits): Stop using > __is_void. > * include/bits/cpp_type_traits.h (__is_void): Remove unused __is_void. > * include/std/type_traits (is_void_v): Use __is_void built-in > trait. > > Signed-off-by: Ken Matsui > --- > gcc/cp/constraint.cc | 3 ++ > gcc/cp/cp-trait.def | 1 + > gcc/cp/semantics.cc | 4 +++ > gcc/testsuite/g++.dg/ext/has-builtin-1.C | 3 ++ > gcc/testsuite/g++.dg/ext/is_void.C | 35 +++++++++++++++++++ > gcc/testsuite/g++.dg/tm/pr46567.C | 6 ++-- > libstdc++-v3/include/bits/cpp_type_traits.h | 15 -------- > libstdc++-v3/include/debug/helper_functions.h | 5 ++- > libstdc++-v3/include/std/type_traits | 6 ++++ > 9 files changed, 57 insertions(+), 21 deletions(-) > create mode 100644 gcc/testsuite/g++.dg/ext/is_void.C > > diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc > index 927605c6cb7..e8cd98eb2c7 100644 > --- a/gcc/cp/constraint.cc > +++ b/gcc/cp/constraint.cc > @@ -3757,6 +3757,9 @@ diagnose_trait_expr (tree expr, tree args) > case CPTK_IS_FUNCTION: > inform (loc, " %qT is not a function", t1); > break; > + case CPTK_IS_VOID: > + inform (loc, " %qT is not a void type", t1); > + break; > case CPTK_IS_AGGREGATE: > inform (loc, " %qT is not an aggregate", t1); > break; > diff --git a/gcc/cp/cp-trait.def b/gcc/cp/cp-trait.def > index 3cd3babc242..8e76668f6ed 100644 > --- a/gcc/cp/cp-trait.def > +++ b/gcc/cp/cp-trait.def > @@ -84,6 +84,7 @@ DEFTRAIT_EXPR (IS_TRIVIALLY_CONSTRUCTIBLE, "__is_trivially_constructible", -1) > DEFTRAIT_EXPR (IS_TRIVIALLY_COPYABLE, "__is_trivially_copyable", 1) > DEFTRAIT_EXPR (IS_UNION, "__is_union", 1) > DEFTRAIT_EXPR (IS_FUNCTION, "__is_function", 1) > +DEFTRAIT_EXPR (IS_VOID, "__is_void", 1) > DEFTRAIT_EXPR (REF_CONSTRUCTS_FROM_TEMPORARY, "__reference_constructs_from_temporary", 2) > DEFTRAIT_EXPR (REF_CONVERTS_FROM_TEMPORARY, "__reference_converts_from_temporary", 2) > /* FIXME Added space to avoid direct usage in GCC 13. */ > diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc > index b976633645a..c4d44413dce 100644 > --- a/gcc/cp/semantics.cc > +++ b/gcc/cp/semantics.cc > @@ -12075,6 +12075,9 @@ trait_expr_value (cp_trait_kind kind, tree type1, tree type2) > case CPTK_IS_FUNCTION: > return type_code1 == FUNCTION_TYPE; > > + case CPTK_IS_VOID: > + return VOID_TYPE_P (type1); > + > case CPTK_IS_FINAL: > return CLASS_TYPE_P (type1) && CLASSTYPE_FINAL (type1); > > @@ -12297,6 +12300,7 @@ finish_trait_expr (location_t loc, cp_trait_kind kind, tree type1, tree type2) > case CPTK_IS_SAME: > case CPTK_IS_REFERENCE: > case CPTK_IS_FUNCTION: > + case CPTK_IS_VOID: > break; > > case CPTK_IS_LAYOUT_COMPATIBLE: > diff --git a/gcc/testsuite/g++.dg/ext/has-builtin-1.C b/gcc/testsuite/g++.dg/ext/has-builtin-1.C > index 90eb00ebf2d..b96cc9e6f50 100644 > --- a/gcc/testsuite/g++.dg/ext/has-builtin-1.C > +++ b/gcc/testsuite/g++.dg/ext/has-builtin-1.C > @@ -152,3 +152,6 @@ > #if !__has_builtin (__is_function) > # error "__has_builtin (__is_function) failed" > #endif > +#if !__has_builtin (__is_void) > +# error "__has_builtin (__is_void) failed" > +#endif > diff --git a/gcc/testsuite/g++.dg/ext/is_void.C b/gcc/testsuite/g++.dg/ext/is_void.C > new file mode 100644 > index 00000000000..707f0d6875b > --- /dev/null > +++ b/gcc/testsuite/g++.dg/ext/is_void.C > @@ -0,0 +1,35 @@ > +// { dg-do compile { target c++11 } } > + > +#include > + > +using namespace __gnu_test; > + > +#define SA(X) static_assert((X),#X) > +#define SA_TEST_CATEGORY(TRAIT, TYPE, EXPECT) \ > + SA(TRAIT(TYPE) == EXPECT); \ > + SA(TRAIT(const TYPE) == EXPECT); \ > + SA(TRAIT(volatile TYPE) == EXPECT); \ > + SA(TRAIT(const volatile TYPE) == EXPECT) > + > +SA_TEST_CATEGORY(__is_void, void, true); > + > +SA_TEST_CATEGORY(__is_void, char, false); > +SA_TEST_CATEGORY(__is_void, signed char, false); > +SA_TEST_CATEGORY(__is_void, unsigned char, false); > +SA_TEST_CATEGORY(__is_void, wchar_t, false); > +SA_TEST_CATEGORY(__is_void, short, false); > +SA_TEST_CATEGORY(__is_void, unsigned short, false); > +SA_TEST_CATEGORY(__is_void, int, false); > +SA_TEST_CATEGORY(__is_void, unsigned int, false); > +SA_TEST_CATEGORY(__is_void, long, false); > +SA_TEST_CATEGORY(__is_void, unsigned long, false); > +SA_TEST_CATEGORY(__is_void, long long, false); > +SA_TEST_CATEGORY(__is_void, unsigned long long, false); > +SA_TEST_CATEGORY(__is_void, float, false); > +SA_TEST_CATEGORY(__is_void, double, false); > +SA_TEST_CATEGORY(__is_void, long double, false); > + > +// Sanity check. > +SA_TEST_CATEGORY(__is_void, ClassType, false); > +SA_TEST_CATEGORY(__is_void, IncompleteClass, false); > +SA_TEST_CATEGORY(__is_void, IncompleteUnion, false); > diff --git a/gcc/testsuite/g++.dg/tm/pr46567.C b/gcc/testsuite/g++.dg/tm/pr46567.C > index 6d791484448..e689e293bd4 100644 > --- a/gcc/testsuite/g++.dg/tm/pr46567.C > +++ b/gcc/testsuite/g++.dg/tm/pr46567.C > @@ -72,13 +72,13 @@ namespace std __attribute__ ((__visibility__ ("default"))) { > typedef __true_type __type; > }; > template > - struct __is_void > + struct ____is_void > { > enum { __value = 0 }; > typedef __false_type __type; > }; > template<> > - struct __is_void > + struct ____is_void > { > enum { __value = 1 }; > typedef __true_type __type; > @@ -222,7 +222,7 @@ namespace std __attribute__ ((__visibility__ ("default"))) { > { }; > template > struct __is_fundamental > - : public __traitor<__is_void<_Tp>, __is_arithmetic<_Tp> > > + : public __traitor<____is_void<_Tp>, __is_arithmetic<_Tp> > > { }; > template > struct __is_scalar > diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h > index 4312f32a4e0..d329bc5b208 100644 > --- a/libstdc++-v3/include/bits/cpp_type_traits.h > +++ b/libstdc++-v3/include/bits/cpp_type_traits.h > @@ -105,21 +105,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > typedef __true_type __type; > }; > > - // Holds if the template-argument is a void type. > - template > - struct __is_void > - { > - enum { __value = 0 }; > - typedef __false_type __type; > - }; > - > - template<> > - struct __is_void > - { > - enum { __value = 1 }; > - typedef __true_type __type; > - }; > - > // > // Integer types > // > diff --git a/libstdc++-v3/include/debug/helper_functions.h b/libstdc++-v3/include/debug/helper_functions.h > index dccf8e9e5e6..66b4e9e1ecf 100644 > --- a/libstdc++-v3/include/debug/helper_functions.h > +++ b/libstdc++-v3/include/debug/helper_functions.h > @@ -66,13 +66,12 @@ namespace __gnu_debug > typedef > typename std::iterator_traits<_Iterator>::difference_type _ItDiffType; > > - template - typename = typename std::__is_void<_DiffType>::__type> > + template > struct _DiffTraits > { typedef _DiffType __type; }; > > template > - struct _DiffTraits<_DiffType, std::__true_type> > + struct _DiffTraits<_DiffType, void> > { typedef std::ptrdiff_t __type; }; > > typedef typename _DiffTraits<_ItDiffType>::__type _DiffType; > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits > index 954b57518de..780fcc00135 100644 > --- a/libstdc++-v3/include/std/type_traits > +++ b/libstdc++-v3/include/std/type_traits > @@ -3166,8 +3166,14 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > * @{ > * @ingroup variable_templates > */ > +#if __has_builtin(__is_void) > +template > + inline constexpr bool is_void_v = __is_void(_Tp); > +#else > template > inline constexpr bool is_void_v = is_void<_Tp>::value; > +#endif We should instead optimize this the way we do for the class template, by defining 4 explicit specializations of is_void_v. > + > template > inline constexpr bool is_null_pointer_v = is_null_pointer<_Tp>::value; > template > -- > 2.41.0 > >