* [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed @ 2022-10-10 11:20 Jonathan Wakely 2022-10-10 13:09 ` Patrick Palka 0 siblings, 1 reply; 5+ messages in thread From: Jonathan Wakely @ 2022-10-10 11:20 UTC (permalink / raw) To: libstdc++, gcc-patches Tested powerpc64le-linux. Pushed to trunk. -- >8 -- Currently we only reject std::make_signed_t<bool> but not cv bool. Similarly for std::make_unsigned_t<cv bool>. As well as making those ill-formed, this adds a requires-clause to the make_signed and make_unsigned primary templates. This makes non-integral, non-enum cases fail immediately with a clear error, rather than giving an error about __make_signed_selector<T, false, false> being incomplete. libstdc++-v3/ChangeLog: * include/std/type_traits (make_signed, make_unsigned): Add specializations for cv bool. Add requires-clause for C++20 to improve diagnostics for non-integral, non-enum cases. * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Check cv bool. * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Likewise. * testsuite/24_iterators/range_access/range_access_cpp20_neg.cc: Adjust expected errors for C++20 and later. * testsuite/lib/prune.exp: Prune "in requirements [with ...]" lines from diagnostics. --- libstdc++-v3/include/std/type_traits | 18 ++++++++++--- .../make_signed/requirements/typedefs_neg.cc | 27 +++++++++---------- .../requirements/typedefs_neg.cc | 25 ++++++++--------- .../range_access/range_access_cpp20_neg.cc | 3 ++- libstdc++-v3/testsuite/lib/prune.exp | 1 + 5 files changed, 40 insertions(+), 34 deletions(-) diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index b74565eb521..6108b98aa6a 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -1802,12 +1802,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Primary template. /// make_unsigned template<typename _Tp> +#if __cpp_concepts + requires is_integral<_Tp>::value || __is_enum(_Tp) +#endif struct make_unsigned { typedef typename __make_unsigned_selector<_Tp>::__type type; }; // Integral, but don't define. - template<> - struct make_unsigned<bool>; + template<> struct make_unsigned<bool>; + template<> struct make_unsigned<bool const>; + template<> struct make_unsigned<bool volatile>; + template<> struct make_unsigned<bool const volatile>; /// @cond undocumented @@ -1932,12 +1937,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Primary template. /// make_signed template<typename _Tp> +#if __cpp_concepts + requires is_integral<_Tp>::value || __is_enum(_Tp) +#endif struct make_signed { typedef typename __make_signed_selector<_Tp>::__type type; }; // Integral, but don't define. - template<> - struct make_signed<bool>; + template<> struct make_signed<bool>; + template<> struct make_signed<bool const>; + template<> struct make_signed<bool volatile>; + template<> struct make_signed<bool const volatile>; #if __cplusplus > 201103L /// Alias template for make_signed diff --git a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc index 051bb64c710..88b8ae887ef 100644 --- a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc +++ b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc @@ -20,31 +20,28 @@ // <http://www.gnu.org/licenses/>. #include <type_traits> -#include <testsuite_character.h> -enum test_enum { first_selection }; +struct pod_class { }; void test01() { using std::make_signed; // Negative tests. - typedef make_signed<bool>::type test1_type; + using T1 = make_signed<bool>::type; // { dg-error "incomplete" } + using T2 = make_signed<const bool>::type; // { dg-error "incomplete" } + using T3 = make_signed<volatile bool>::type; // { dg-error "incomplete" } + using T4 = make_signed<const volatile bool>::type; // { dg-error "incomplete" } - typedef make_signed<__gnu_test::pod_uint>::type test2_type; + using T5 = make_signed<pod_class>::type; // { dg-error "here" } - typedef make_signed<int[4]>::type test3_type; + using T6 = make_signed<int[4]>::type; // { dg-error "here" } - typedef void (fn_type) (); - typedef make_signed<fn_type>::type test4_type; + using fn_type = void (); + using T7 = make_signed<fn_type>::type; // { dg-error "here" } - typedef make_signed<float>::type test5_type; + using T8 = make_signed<float>::type; // { dg-error "here" } } -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 32 } -// { dg-error "required from here" "" { target *-*-* } 34 } -// { dg-error "required from here" "" { target *-*-* } 36 } -// { dg-error "required from here" "" { target *-*-* } 39 } -// { dg-error "required from here" "" { target *-*-* } 41 } - -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } +// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } +// { dg-error "constraint failure" "" { target c++20 } 0 } diff --git a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc index ff98cc42ef7..50f15e7037c 100644 --- a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc +++ b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc @@ -21,7 +21,6 @@ #include <type_traits> -enum test_enum { first_selection }; struct pod_class { }; void test01() @@ -29,22 +28,20 @@ void test01() using std::make_unsigned; // Negative tests. - typedef make_unsigned<bool>::type test1_type; + using T1 = make_unsigned<bool>::type; // { dg-error "incomplete" } + using T2 = make_unsigned<const bool>::type; // { dg-error "incomplete" } + using T3 = make_unsigned<volatile bool>::type; // { dg-error "incomplete" } + using T4 = make_unsigned<const volatile bool>::type; // { dg-error "incomplete" } - typedef make_unsigned<pod_class>::type test2_type; + using T5 = make_unsigned<pod_class>::type; // { dg-error "here" } - typedef make_unsigned<int[4]>::type test3_type; + using T6 = make_unsigned<int[4]>::type; // { dg-error "here" } - typedef void (fn_type) (); - typedef make_unsigned<fn_type>::type test4_type; + using fn_type = void (); + using T7 = make_unsigned<fn_type>::type; // { dg-error "here" } - typedef make_unsigned<float>::type test5_type; + using T8 = make_unsigned<float>::type; // { dg-error "here" } } -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 32 } -// { dg-error "required from here" "" { target *-*-* } 34 } -// { dg-error "required from here" "" { target *-*-* } 36 } -// { dg-error "required from here" "" { target *-*-* } 39 } -// { dg-error "required from here" "" { target *-*-* } 41 } - -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } +// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } +// { dg-error "constraint failure" "" { target c++20 } 0 } diff --git a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc index c0825a58587..26c8ae0ee1e 100644 --- a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc +++ b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc @@ -46,4 +46,5 @@ test03() C c; std::ssize(c); // { dg-error "no matching function" } } -// { dg-error "incomplete type .*make_signed.*S" "" { target *-*-* } 0 } +// { dg-error "incomplete type .*make_signed.*S" "" { target c++17_down } 0 } +// { dg-error "constraint failure" "" { target c++20 } 0 } diff --git a/libstdc++-v3/testsuite/lib/prune.exp b/libstdc++-v3/testsuite/lib/prune.exp index d457e975218..6d0b77a8ccd 100644 --- a/libstdc++-v3/testsuite/lib/prune.exp +++ b/libstdc++-v3/testsuite/lib/prune.exp @@ -51,6 +51,7 @@ proc libstdc++-dg-prune { system text } { regsub -all "(^|\n)\[^\n\]*: (recursively )?required \[^\n\]*" $text "" text regsub -all "(^|\n)\[^\n\]*: . skipping \[0-9\]* instantiation contexts \[^\n\]*" $text "" text regsub -all "(^|\n)\[^\n\]*: in .constexpr. expansion \[^\n\]*" $text "" text + regsub -all "(^|\n)\[^\n\]*: in requirements .with\[^\n\]*" $text "" text regsub -all "(^|\n) inlined from \[^\n\]*" $text "" text # Why doesn't GCC need these to strip header context? regsub -all "(^|\n)In file included from \[^\n\]*" $text "" text -- 2.37.3 ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed 2022-10-10 11:20 [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed Jonathan Wakely @ 2022-10-10 13:09 ` Patrick Palka 2022-10-10 13:49 ` Tim Song 0 siblings, 1 reply; 5+ messages in thread From: Patrick Palka @ 2022-10-10 13:09 UTC (permalink / raw) To: Jonathan Wakely; +Cc: libstdc++, gcc-patches On Mon, 10 Oct 2022, Jonathan Wakely via Libstdc++ wrote: > Tested powerpc64le-linux. Pushed to trunk. > > -- >8 -- > > Currently we only reject std::make_signed_t<bool> but not cv bool. > Similarly for std::make_unsigned_t<cv bool>. > > As well as making those ill-formed, this adds a requires-clause to the > make_signed and make_unsigned primary templates. This makes > non-integral, non-enum cases fail immediately with a clear error, rather > than giving an error about __make_signed_selector<T, false, false> being > incomplete. IIUC the requires-clause turns what was once a hard error into a SFINAE error, so e.g. for template<class T> typename make_signed<T>::type f(int); template<class T> void f(...); int main() { f<void>(0); } the call to f would previously be rejected due to an error outside the immediate context about incomplete __make_signed_selector, and now with the requires-clause resolves to the second overload. I wonder if this new behavior is conforming -- the examples in [structure.specifications] of how to implement 'Mandates' suggest that a failed 'Mandates' should yield a hard error? > > libstdc++-v3/ChangeLog: > > * include/std/type_traits (make_signed, make_unsigned): Add > specializations for cv bool. Add requires-clause for C++20 to > improve diagnostics for non-integral, non-enum cases. > * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: > Check cv bool. > * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: > Likewise. > * testsuite/24_iterators/range_access/range_access_cpp20_neg.cc: > Adjust expected errors for C++20 and later. > * testsuite/lib/prune.exp: Prune "in requirements [with ...]" > lines from diagnostics. > --- > libstdc++-v3/include/std/type_traits | 18 ++++++++++--- > .../make_signed/requirements/typedefs_neg.cc | 27 +++++++++---------- > .../requirements/typedefs_neg.cc | 25 ++++++++--------- > .../range_access/range_access_cpp20_neg.cc | 3 ++- > libstdc++-v3/testsuite/lib/prune.exp | 1 + > 5 files changed, 40 insertions(+), 34 deletions(-) > > diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits > index b74565eb521..6108b98aa6a 100644 > --- a/libstdc++-v3/include/std/type_traits > +++ b/libstdc++-v3/include/std/type_traits > @@ -1802,12 +1802,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > // Primary template. > /// make_unsigned > template<typename _Tp> > +#if __cpp_concepts > + requires is_integral<_Tp>::value || __is_enum(_Tp) > +#endif > struct make_unsigned > { typedef typename __make_unsigned_selector<_Tp>::__type type; }; > > // Integral, but don't define. > - template<> > - struct make_unsigned<bool>; > + template<> struct make_unsigned<bool>; > + template<> struct make_unsigned<bool const>; > + template<> struct make_unsigned<bool volatile>; > + template<> struct make_unsigned<bool const volatile>; > > /// @cond undocumented > > @@ -1932,12 +1937,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION > // Primary template. > /// make_signed > template<typename _Tp> > +#if __cpp_concepts > + requires is_integral<_Tp>::value || __is_enum(_Tp) > +#endif > struct make_signed > { typedef typename __make_signed_selector<_Tp>::__type type; }; > > // Integral, but don't define. > - template<> > - struct make_signed<bool>; > + template<> struct make_signed<bool>; > + template<> struct make_signed<bool const>; > + template<> struct make_signed<bool volatile>; > + template<> struct make_signed<bool const volatile>; > > #if __cplusplus > 201103L > /// Alias template for make_signed > diff --git a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc > index 051bb64c710..88b8ae887ef 100644 > --- a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc > +++ b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc > @@ -20,31 +20,28 @@ > // <http://www.gnu.org/licenses/>. > > #include <type_traits> > -#include <testsuite_character.h> > > -enum test_enum { first_selection }; > +struct pod_class { }; > > void test01() > { > using std::make_signed; > > // Negative tests. > - typedef make_signed<bool>::type test1_type; > + using T1 = make_signed<bool>::type; // { dg-error "incomplete" } > + using T2 = make_signed<const bool>::type; // { dg-error "incomplete" } > + using T3 = make_signed<volatile bool>::type; // { dg-error "incomplete" } > + using T4 = make_signed<const volatile bool>::type; // { dg-error "incomplete" } > > - typedef make_signed<__gnu_test::pod_uint>::type test2_type; > + using T5 = make_signed<pod_class>::type; // { dg-error "here" } > > - typedef make_signed<int[4]>::type test3_type; > + using T6 = make_signed<int[4]>::type; // { dg-error "here" } > > - typedef void (fn_type) (); > - typedef make_signed<fn_type>::type test4_type; > + using fn_type = void (); > + using T7 = make_signed<fn_type>::type; // { dg-error "here" } > > - typedef make_signed<float>::type test5_type; > + using T8 = make_signed<float>::type; // { dg-error "here" } > } > > -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 32 } > -// { dg-error "required from here" "" { target *-*-* } 34 } > -// { dg-error "required from here" "" { target *-*-* } 36 } > -// { dg-error "required from here" "" { target *-*-* } 39 } > -// { dg-error "required from here" "" { target *-*-* } 41 } > - > -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } > +// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } > +// { dg-error "constraint failure" "" { target c++20 } 0 } > diff --git a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc > index ff98cc42ef7..50f15e7037c 100644 > --- a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc > +++ b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc > @@ -21,7 +21,6 @@ > > #include <type_traits> > > -enum test_enum { first_selection }; > struct pod_class { }; > > void test01() > @@ -29,22 +28,20 @@ void test01() > using std::make_unsigned; > > // Negative tests. > - typedef make_unsigned<bool>::type test1_type; > + using T1 = make_unsigned<bool>::type; // { dg-error "incomplete" } > + using T2 = make_unsigned<const bool>::type; // { dg-error "incomplete" } > + using T3 = make_unsigned<volatile bool>::type; // { dg-error "incomplete" } > + using T4 = make_unsigned<const volatile bool>::type; // { dg-error "incomplete" } > > - typedef make_unsigned<pod_class>::type test2_type; > + using T5 = make_unsigned<pod_class>::type; // { dg-error "here" } > > - typedef make_unsigned<int[4]>::type test3_type; > + using T6 = make_unsigned<int[4]>::type; // { dg-error "here" } > > - typedef void (fn_type) (); > - typedef make_unsigned<fn_type>::type test4_type; > + using fn_type = void (); > + using T7 = make_unsigned<fn_type>::type; // { dg-error "here" } > > - typedef make_unsigned<float>::type test5_type; > + using T8 = make_unsigned<float>::type; // { dg-error "here" } > } > > -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 32 } > -// { dg-error "required from here" "" { target *-*-* } 34 } > -// { dg-error "required from here" "" { target *-*-* } 36 } > -// { dg-error "required from here" "" { target *-*-* } 39 } > -// { dg-error "required from here" "" { target *-*-* } 41 } > - > -// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } > +// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } > +// { dg-error "constraint failure" "" { target c++20 } 0 } > diff --git a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc > index c0825a58587..26c8ae0ee1e 100644 > --- a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc > +++ b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc > @@ -46,4 +46,5 @@ test03() > C c; > std::ssize(c); // { dg-error "no matching function" } > } > -// { dg-error "incomplete type .*make_signed.*S" "" { target *-*-* } 0 } > +// { dg-error "incomplete type .*make_signed.*S" "" { target c++17_down } 0 } > +// { dg-error "constraint failure" "" { target c++20 } 0 } > diff --git a/libstdc++-v3/testsuite/lib/prune.exp b/libstdc++-v3/testsuite/lib/prune.exp > index d457e975218..6d0b77a8ccd 100644 > --- a/libstdc++-v3/testsuite/lib/prune.exp > +++ b/libstdc++-v3/testsuite/lib/prune.exp > @@ -51,6 +51,7 @@ proc libstdc++-dg-prune { system text } { > regsub -all "(^|\n)\[^\n\]*: (recursively )?required \[^\n\]*" $text "" text > regsub -all "(^|\n)\[^\n\]*: . skipping \[0-9\]* instantiation contexts \[^\n\]*" $text "" text > regsub -all "(^|\n)\[^\n\]*: in .constexpr. expansion \[^\n\]*" $text "" text > + regsub -all "(^|\n)\[^\n\]*: in requirements .with\[^\n\]*" $text "" text > regsub -all "(^|\n) inlined from \[^\n\]*" $text "" text > # Why doesn't GCC need these to strip header context? > regsub -all "(^|\n)In file included from \[^\n\]*" $text "" text > -- > 2.37.3 > > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed 2022-10-10 13:09 ` Patrick Palka @ 2022-10-10 13:49 ` Tim Song 2022-10-10 14:05 ` Jonathan Wakely 0 siblings, 1 reply; 5+ messages in thread From: Tim Song @ 2022-10-10 13:49 UTC (permalink / raw) To: Patrick Palka; +Cc: Jonathan Wakely, libstdc++, gcc-patches On Mon, Oct 10, 2022 at 8:09 AM Patrick Palka via Libstdc++ <libstdc++@gcc.gnu.org> wrote: > > On Mon, 10 Oct 2022, Jonathan Wakely via Libstdc++ wrote: > > > Tested powerpc64le-linux. Pushed to trunk. > > > > -- >8 -- > > > > Currently we only reject std::make_signed_t<bool> but not cv bool. > > Similarly for std::make_unsigned_t<cv bool>. > > > > As well as making those ill-formed, this adds a requires-clause to the > > make_signed and make_unsigned primary templates. This makes > > non-integral, non-enum cases fail immediately with a clear error, rather > > than giving an error about __make_signed_selector<T, false, false> being > > incomplete. > > IIUC the requires-clause turns what was once a hard error into a SFINAE > error, so e.g. for > > template<class T> typename make_signed<T>::type f(int); > template<class T> void f(...); > int main() { f<void>(0); } > > the call to f would previously be rejected due to an error outside the > immediate context about incomplete __make_signed_selector, and now with > the requires-clause resolves to the second overload. I wonder if this > new behavior is conforming -- the examples in [structure.specifications] > of how to implement 'Mandates' suggest that a failed 'Mandates' should > yield a hard error? I'm also concerned about the inability to name make_signed<X> in a context that doesn't require its instantiation (e.g., conditional_t<is_integral_v<T>, make_signed<T>, type_identity<T>>::type). That seems a plausible use case, and breaking it doesn't seem great to me (conformance aside). ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed 2022-10-10 13:49 ` Tim Song @ 2022-10-10 14:05 ` Jonathan Wakely 2022-10-10 20:38 ` Jonathan Wakely 0 siblings, 1 reply; 5+ messages in thread From: Jonathan Wakely @ 2022-10-10 14:05 UTC (permalink / raw) To: Tim Song; +Cc: Patrick Palka, libstdc++, gcc-patches On Mon, 10 Oct 2022 at 14:50, Tim Song via Libstdc++ <libstdc++@gcc.gnu.org> wrote: > > On Mon, Oct 10, 2022 at 8:09 AM Patrick Palka via Libstdc++ > <libstdc++@gcc.gnu.org> wrote: > > > > On Mon, 10 Oct 2022, Jonathan Wakely via Libstdc++ wrote: > > > > > Tested powerpc64le-linux. Pushed to trunk. > > > > > > -- >8 -- > > > > > > Currently we only reject std::make_signed_t<bool> but not cv bool. > > > Similarly for std::make_unsigned_t<cv bool>. > > > > > > As well as making those ill-formed, this adds a requires-clause to the > > > make_signed and make_unsigned primary templates. This makes > > > non-integral, non-enum cases fail immediately with a clear error, rather > > > than giving an error about __make_signed_selector<T, false, false> being > > > incomplete. > > > > IIUC the requires-clause turns what was once a hard error into a SFINAE > > error, so e.g. for > > > > template<class T> typename make_signed<T>::type f(int); > > template<class T> void f(...); > > int main() { f<void>(0); } > > > > the call to f would previously be rejected due to an error outside the > > immediate context about incomplete __make_signed_selector, and now with > > the requires-clause resolves to the second overload. I wonder if this > > new behavior is conforming -- the examples in [structure.specifications] > > of how to implement 'Mandates' suggest that a failed 'Mandates' should > > yield a hard error? > > I'm also concerned about the inability to name make_signed<X> in a > context that doesn't require its instantiation (e.g., > conditional_t<is_integral_v<T>, make_signed<T>, > type_identity<T>>::type). That seems a plausible use case, and > breaking it doesn't seem great to me (conformance aside). Ah yes, that's a problem. We could fix it like this: template<typename _Tp> struct make_unsigned; template<typename _Tp> #if __cpp_concepts requires is_integral<_Tp>::value || __is_enum(_Tp) struct make_unsigned<_Tp> #else struct make_unsigned #endif { typedef typename __make_unsigned_selector<_Tp>::__type type; }; But that doesn't really improve the diagnostic much. It's simpler just to revert the addition of the constraints. ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed 2022-10-10 14:05 ` Jonathan Wakely @ 2022-10-10 20:38 ` Jonathan Wakely 0 siblings, 0 replies; 5+ messages in thread From: Jonathan Wakely @ 2022-10-10 20:38 UTC (permalink / raw) To: Tim Song; +Cc: Patrick Palka, libstdc++, gcc-patches [-- Attachment #1: Type: text/plain, Size: 2415 bytes --] On Mon, 10 Oct 2022 at 15:05, Jonathan Wakely wrote: > > On Mon, 10 Oct 2022 at 14:50, Tim Song via Libstdc++ > <libstdc++@gcc.gnu.org> wrote: > > > > On Mon, Oct 10, 2022 at 8:09 AM Patrick Palka via Libstdc++ > > <libstdc++@gcc.gnu.org> wrote: > > > > > > On Mon, 10 Oct 2022, Jonathan Wakely via Libstdc++ wrote: > > > > > > > Tested powerpc64le-linux. Pushed to trunk. > > > > > > > > -- >8 -- > > > > > > > > Currently we only reject std::make_signed_t<bool> but not cv bool. > > > > Similarly for std::make_unsigned_t<cv bool>. > > > > > > > > As well as making those ill-formed, this adds a requires-clause to the > > > > make_signed and make_unsigned primary templates. This makes > > > > non-integral, non-enum cases fail immediately with a clear error, rather > > > > than giving an error about __make_signed_selector<T, false, false> being > > > > incomplete. > > > > > > IIUC the requires-clause turns what was once a hard error into a SFINAE > > > error, so e.g. for > > > > > > template<class T> typename make_signed<T>::type f(int); > > > template<class T> void f(...); > > > int main() { f<void>(0); } > > > > > > the call to f would previously be rejected due to an error outside the > > > immediate context about incomplete __make_signed_selector, and now with > > > the requires-clause resolves to the second overload. I wonder if this > > > new behavior is conforming -- the examples in [structure.specifications] > > > of how to implement 'Mandates' suggest that a failed 'Mandates' should > > > yield a hard error? > > > > I'm also concerned about the inability to name make_signed<X> in a > > context that doesn't require its instantiation (e.g., > > conditional_t<is_integral_v<T>, make_signed<T>, > > type_identity<T>>::type). That seems a plausible use case, and > > breaking it doesn't seem great to me (conformance aside). > > Ah yes, that's a problem. > > We could fix it like this: > > template<typename _Tp> > struct make_unsigned; > > template<typename _Tp> > #if __cpp_concepts > requires is_integral<_Tp>::value || __is_enum(_Tp) > struct make_unsigned<_Tp> > #else > struct make_unsigned > #endif > { typedef typename __make_unsigned_selector<_Tp>::__type type; }; > > But that doesn't really improve the diagnostic much. It's simpler > just to revert the addition of the constraints. Reverted like so. Tested powerpc64le-linux, pushed to trunk. [-- Attachment #2: patch.txt --] [-- Type: text/plain, Size: 4984 bytes --] commit 1d2f07ed4ce028a7c1f9b18f5d959f30213545ca Author: Jonathan Wakely <jwakely@redhat.com> Date: Mon Oct 10 15:06:53 2022 libstdc++: Revert addition of constraints to make_signed/make_unsigned Constraining the primary template makes it unusable in uninstantiated contexts. libstdc++-v3/ChangeLog: * include/std/type_traits (make_signed, make_unsigned): Remove constraints on primary template. * testsuite/20_util/make_signed/requirements/typedefs_neg.cc: Undo changes to expected error in C++20 mode. * testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc: Likewise. * testsuite/24_iterators/range_access/range_access_cpp20_neg.cc: Likewise. * testsuite/20_util/make_signed/requirements/uninstantiated.cc: New test. * testsuite/20_util/make_unsigned/requirements/uninstantiated.cc: New test. diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits index 6108b98aa6a..1d7c3b04a0e 100644 --- a/libstdc++-v3/include/std/type_traits +++ b/libstdc++-v3/include/std/type_traits @@ -1802,9 +1802,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Primary template. /// make_unsigned template<typename _Tp> -#if __cpp_concepts - requires is_integral<_Tp>::value || __is_enum(_Tp) -#endif struct make_unsigned { typedef typename __make_unsigned_selector<_Tp>::__type type; }; @@ -1937,9 +1934,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION // Primary template. /// make_signed template<typename _Tp> -#if __cpp_concepts - requires is_integral<_Tp>::value || __is_enum(_Tp) -#endif struct make_signed { typedef typename __make_signed_selector<_Tp>::__type type; }; diff --git a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc index 88b8ae887ef..451eeb8c92d 100644 --- a/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc +++ b/libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc @@ -43,5 +43,4 @@ void test01() using T8 = make_signed<float>::type; // { dg-error "here" } } -// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } -// { dg-error "constraint failure" "" { target c++20 } 0 } +// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } diff --git a/libstdc++-v3/testsuite/20_util/make_signed/requirements/uninstantiated.cc b/libstdc++-v3/testsuite/20_util/make_signed/requirements/uninstantiated.cc new file mode 100644 index 00000000000..3facf0c595a --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/make_signed/requirements/uninstantiated.cc @@ -0,0 +1,8 @@ +// { dg-do compile { target c++11 } } +#include <type_traits> + +// Check that we can name invalid specializations, just don't instantiate them. + +using X = std::make_signed<float>; +using Y = std::make_signed<bool>; +using Z = std::make_signed<void>; diff --git a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc index 50f15e7037c..49d520936a3 100644 --- a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc +++ b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc @@ -43,5 +43,4 @@ void test01() using T8 = make_unsigned<float>::type; // { dg-error "here" } } -// { dg-error "invalid use of incomplete type" "" { target c++17_down } 0 } -// { dg-error "constraint failure" "" { target c++20 } 0 } +// { dg-error "invalid use of incomplete type" "" { target *-*-* } 0 } diff --git a/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/uninstantiated.cc b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/uninstantiated.cc new file mode 100644 index 00000000000..9b860967379 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/make_unsigned/requirements/uninstantiated.cc @@ -0,0 +1,8 @@ +// { dg-do compile { target c++11 } } +#include <type_traits> + +// Check that we can name invalid specializations, just don't instantiate them. + +using X = std::make_unsigned<float>; +using Y = std::make_unsigned<bool>; +using Z = std::make_unsigned<void>; diff --git a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc index 26c8ae0ee1e..c0825a58587 100644 --- a/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc +++ b/libstdc++-v3/testsuite/24_iterators/range_access/range_access_cpp20_neg.cc @@ -46,5 +46,4 @@ test03() C c; std::ssize(c); // { dg-error "no matching function" } } -// { dg-error "incomplete type .*make_signed.*S" "" { target c++17_down } 0 } -// { dg-error "constraint failure" "" { target c++20 } 0 } +// { dg-error "incomplete type .*make_signed.*S" "" { target *-*-* } 0 } ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-10-10 20:38 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-10-10 11:20 [committed] libstdc++: std::make_signed_t<cv bool> should be ill-formed Jonathan Wakely 2022-10-10 13:09 ` Patrick Palka 2022-10-10 13:49 ` Tim Song 2022-10-10 14:05 ` Jonathan Wakely 2022-10-10 20:38 ` Jonathan Wakely
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