On 11/05/21 21:27 +0300, Antony Polukhin via Libstdc++ wrote:
This patch provides compile time diagnostics for common misuse of
[locale.convenience] functions with std::string as a character type.
2021-05-11 Antony Polukhin <antosh...@gmail.com>
PR libstdc++/89728
* include/bits/locale_facets.h (ctype) Add static assert.
* testsuite/22_locale/ctype/is/string/89728_neg.cc New test.
--
Best regards,
Antony Polukhin
diff --git a/libstdc++-v3/include/bits/locale_facets.h
b/libstdc++-v3/include/bits/locale_facets.h
index 03724cf..012857f 100644
--- a/libstdc++-v3/include/bits/locale_facets.h
+++ b/libstdc++-v3/include/bits/locale_facets.h
@@ -136,6 +136,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __s;
}
+ template<typename>
+ struct __is_string
+ {
+ enum _Value { _value = 0 };
The _value member needs to use double underscores.
But since this is only used in a static_assert, which is only
available in C++11, I think it can just derive from std::false_type
instead.
+ };
+
+ template<typename _CharT, typename _Traits, typename _Alloc>
+ struct __is_string<basic_string<_CharT, _Traits, _Alloc> >
+ {
+ enum _Value { _value = 1 };
+ };
// 22.2.1.1 Template class ctype
// Include host and configuration specific ctype enums for ctype_base.
@@ -614,6 +625,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<typename _CharT>
class ctype : public __ctype_abstract_base<_CharT>
{
+#if __cplusplus >= 201103L
+ static_assert(!__is_string<_CharT>::_value,
+ "std::basic_string used as a character type");
+#endif
public:
// Types:
typedef _CharT char_type;
Alternatively, would it be even simpler to just define a partial
specialization of ctype?
template<typename _CharT, typename _Traits, typename _Alloc>
class ctype<basic_string<_CharT, _Traits, _Alloc> >
{
#if __cplusplus >= 201103L
static_assert(something dependent,
"std::basic_string used as a character type");
#endif
private:
ctype();
~ctype();
};
This will work in C++98 too.
