Re: [PATCH] PR libstdc++/89728 diagnose some missuses of [locale.convenience] functions

[Antony Polukhin <antoshkka@gmail.com>]

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ср, 12 мая 2021 г. в 18:38, Antony Polukhin <antoshkka@gmail.com>:
>
> ср, 12 мая 2021 г. в 17:44, Jonathan Wakely <jwakely@redhat.com>:
> >
> > On 12/05/21 12:58 +0300, Antony Polukhin wrote:
> > >ср, 12 мая 2021 г. в 12:18, Jonathan Wakely <jwakely@redhat.com>:
> > ><...>
> > >> Or just leave it undefined, as libc++ seems to do according to your
> > >> comment in PR 89728:
> > >>
> > >> error: implicit instantiation of undefined template 'std::__1::ctype<std::__1::basic_string<char> >'
> > >>
> > >> Was your aim to have a static_assert that gives a more descriptive
> > >> error? We could leave it undefined in C++98 and have the static assert
> > >> for C++11 and up.
> > >
> > >Leaving it undefined would be the best. It would allow SFINAE on ctype
> > >and a compile time error is informative enough.
> > >
> > >However, there may be users who instantiate ctype<ThierChar> in a
> > >shared library without ctype<ThierChar> template specializations in
> > >the main executable. Making the default ctype undefined would break
> > >their compilation:
> > >
> > >#include <locale>
> > >// no ctype<ThierChar> specialization
> > >c = std::tolower(ThierChar{42}, locale_from_shared_library()); // OK
> > >right now in libstdc++, fails on libc++
> >
> > What I meant was leaving the partial specialization undefined, not the
> > primary template, i.e.
> >
> > --- a/libstdc++-v3/include/bits/locale_facets.h
> > +++ b/libstdc++-v3/include/bits/locale_facets.h
> > @@ -1476,6 +1476,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> >       };
> >   #endif //_GLIBCXX_USE_WCHAR_T
> >
> > +  template<typename _CharT, typename _Traits, typename _Alloc>
> > +    class ctype<basic_string<_CharT, _Traits, _Alloc> >;
> > +
> >     /// class ctype_byname [22.2.1.2].
> >     template<typename _CharT>
> >       class ctype_byname : public ctype<_CharT>
> >
> > This makes your test fail with errors like this:
> >
> > In file included from /home/jwakely/gcc/12/include/c++/12.0.0/locale:40,
> >                   from loc.C:1:
> > /home/jwakely/gcc/12/include/c++/12.0.0/bits/locale_facets.h: In instantiation of 'bool std::isspace(_CharT, const std::locale&) [with _CharT = std::__cxx11::basic_string<char>]':
> > loc.C:16:15:   required from here
> > /home/jwakely/gcc/12/include/c++/12.0.0/bits/locale_facets.h:2600:47: error: invalid use of incomplete type 'const class std::ctype<std::__cxx11::basic_string<char> >'
> >   2600 |     { return use_facet<ctype<_CharT> >(__loc).is(ctype_base::space, __c); }
> >        |              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~
> >
> > But it shouldn't affect the uses of ctype<TheirChar>.
> >
> > What do you think?
>
> Good idea. That way the compiler message points directly to the
> misused function.
>
> Patch is in attachment

Replaced {} with () in test to be C++98 compatible


-- 
Best regards,
Antony Polukhin

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diff --git a/libstdc++-v3/include/bits/locale_facets.h b/libstdc++-v3/include/bits/locale_facets.h
index 03724cf..5ca431e 100644
--- a/libstdc++-v3/include/bits/locale_facets.h
+++ b/libstdc++-v3/include/bits/locale_facets.h
@@ -671,6 +671,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   template<typename _CharT>
     locale::id ctype<_CharT>::id;
 
+  // Incomplete to provide a compile time diagnostics for common misuse
+  // of [locale.convenience] functions with basic_string as a character type.
+  template<typename _CharT, typename _Traits, typename _Alloc>
+    class ctype<basic_string<_CharT, _Traits, _Alloc> >;
+
   /**
    *  @brief  The ctype<char> specialization.
    *  @ingroup locales
diff --git a/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc b/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc
new file mode 100644
index 0000000..9f15620
--- /dev/null
+++ b/libstdc++-v3/testsuite/22_locale/ctype/is/string/89728_neg.cc
@@ -0,0 +1,73 @@
+// { dg-do compile }
+
+// Copyright (C) 2021 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-error "complete" "" { target *-*-* } 0 }
+
+#include <locale>
+
+template <class Char, int I>
+struct trait: std::char_traits<Char> {};
+
+template <class Char, int I>
+std::basic_string<Char, trait<Char, I> > make_str()
+{
+  return std::basic_string<Char, trait<Char, I> >();
+}
+
+void test01()
+{
+  const std::locale& loc = std::locale::classic();
+
+  std::isspace(std::string(), loc);		// { dg-error "required from here" }
+  std::isprint(make_str<char, 0>(), loc);	// { dg-error "required from here" }
+  std::iscntrl(make_str<char, 1>(), loc);	// { dg-error "required from here" }
+  std::isupper(make_str<char, 2>(), loc);	// { dg-error "required from here" }
+  std::islower(make_str<char, 3>(), loc);	// { dg-error "required from here" }
+  std::isalpha(make_str<char, 4>(), loc);	// { dg-error "required from here" }
+  std::isdigit(make_str<char, 5>(), loc);	// { dg-error "required from here" }
+  std::ispunct(make_str<char, 6>(), loc);	// { dg-error "required from here" }
+  std::isxdigit(make_str<char, 7>(), loc);	// { dg-error "required from here" }
+  std::isalnum(make_str<char, 8>(), loc);	// { dg-error "required from here" }
+  std::isgraph(make_str<char, 9>(), loc);	// { dg-error "required from here" }
+  std::isblank(make_str<char, 10>(), loc);	// { dg-error "required from here" }
+  std::toupper(make_str<char, 11>(), loc);	// { dg-error "required from here" }
+  std::tolower(make_str<char, 12>(), loc);	// { dg-error "required from here" }
+}
+
+#ifdef _GLIBCXX_USE_WCHAR_T
+void test02()
+{
+  const std::locale& loc = std::locale::classic();
+
+  std::isspace(std::wstring(), loc);		// { dg-error "required from here" }
+  std::isprint(make_str<wchar_t, 0>(), loc);	// { dg-error "required from here" }
+  std::iscntrl(make_str<wchar_t, 1>(), loc);	// { dg-error "required from here" }
+  std::isupper(make_str<wchar_t, 2>(), loc);	// { dg-error "required from here" }
+  std::islower(make_str<wchar_t, 3>(), loc);	// { dg-error "required from here" }
+  std::isalpha(make_str<wchar_t, 4>(), loc);	// { dg-error "required from here" }
+  std::isdigit(make_str<wchar_t, 5>(), loc);	// { dg-error "required from here" }
+  std::ispunct(make_str<wchar_t, 6>(), loc);	// { dg-error "required from here" }
+  std::isxdigit(make_str<wchar_t, 7>(), loc);	// { dg-error "required from here" }
+  std::isalnum(make_str<wchar_t, 8>(), loc);	// { dg-error "required from here" }
+  std::isgraph(make_str<wchar_t, 9>(), loc);	// { dg-error "required from here" }
+  std::isblank(make_str<wchar_t, 10>(), loc);	// { dg-error "required from here" }
+  std::toupper(make_str<wchar_t, 11>(), loc);	// { dg-error "required from here" }
+  std::tolower(make_str<wchar_t, 12>(), loc);	// { dg-error "required from here" }
+}
+#endif