[gcc r12-844] libstdc++: diagnose some misuses of [locale.convenience] functions [PR 89728]

[Jonathan Wakely]

https://gcc.gnu.org/g:fd89fc77639a63a141dbbc6292dd73e653794d61

commit r12-844-gfd89fc77639a63a141dbbc6292dd73e653794d61
Author: Antony Polukhin <antoshkka@gmail.com>
Date:   Mon May 17 14:58:28 2021 +0100

    libstdc++: diagnose some misuses of [locale.convenience] functions [PR 89728]
    
    This patch provides better diagnostics for common misuse of
    [locale.convenience] functions with std::string as a character type.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/89728
            * include/bits/locale_facets.h (ctype<basic_string<C,T,A>>):
            Declare (but do not define) partial specialization.
            * testsuite/22_locale/ctype/is/string/89728_neg.cc: New test.

Diff:
---
 libstdc++-v3/include/bits/locale_facets.h          |  5 ++
 .../22_locale/ctype/is/string/89728_neg.cc         | 73 ++++++++++++++++++++++
 2 files changed, 78 insertions(+)

diff --git a/libstdc++-v3/include/bits/locale_facets.h b/libstdc++-v3/include/bits/locale_facets.h
index 03724cf7d68..5ca431e1a25 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 00000000000..9f15620c9a8
--- /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