[gcc r15-11383] libstdc++: Fix std module to work with --disable-wchar_t [PR126111]

https://gcc.gnu.org/g:7761e534ffd1d0194c180e5e3ad7630d38336d9a

commit r15-11383-g7761e534ffd1d0194c180e5e3ad7630d38336d9a
Author: Jonathan Wakely <[email protected]>
Date:   Mon Jul 13 17:57:50 2026 +0100

    libstdc++: Fix std module to work with --disable-wchar_t [PR126111]
    
    We should not try to export names which are not declared if GCC is
    configured with --disable-wchar_t.
    
    We should also not define the wide stream aliases in <syncstream> and
    <spanstream>.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/126111
            * include/std/format (__format::__write_escape_seq): Remove
            unnecessary alias declaration.
            * include/std/spanstream (wspanbuf, wispanstream, wospanstream)
            (wspanstream): Only declare for _GLIBCXX_USE_WCHAR_T.
            * include/std/syncstream (wsyncbuf wosyncstream): Likewise.
            * src/c++23/std.cc.in: Add preprocessor checks for
            _GLIBCXX_USE_WCHAR_T to names which depend on it.
    
    Reviewed-by: Tomasz Kamiński <[email protected]>
    
    (cherry picked from commit fb0c03ee7afca608cba0419629184b8f442085e2)

Diff:
---
 libstdc++-v3/include/std/format     |  5 ++---
 libstdc++-v3/include/std/spanstream |  8 +++++++
 libstdc++-v3/include/std/syncstream |  5 +++--
 libstdc++-v3/src/c++23/std.cc.in    | 44 +++++++++++++++++++++++++++++++------
 4 files changed, 50 insertions(+), 12 deletions(-)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 6c9f2743f6b4..68ad367bda5d 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1011,7 +1011,6 @@ namespace __format
     __write_escape_seq(_Out __out, uint_least32_t __val,
 		       basic_string_view<_CharT> __prefix)
     {
-      using _Str_view = basic_string_view<_CharT>;
       constexpr size_t __max = 8;
       char __buf[__max];
       const string_view __narrow(
@@ -1026,10 +1025,10 @@ namespace __format
 #ifdef _GLIBCXX_USE_WCHAR_T
       else
 	{
-	  _CharT __wbuf[__max];
+	  wchar_t __wbuf[__max];
 	  const size_t __n = __narrow.size();
 	  std::__to_wstring_numeric(__narrow.data(), __n, __wbuf);
-	  __out = __format::__write(__out, _Str_view(__wbuf, __n));
+	  __out = __format::__write(__out, wstring_view(__wbuf, __n));
 	}
 #endif
       *__out = _Separators<_CharT>::_S_braces()[1];
diff --git a/libstdc++-v3/include/std/spanstream b/libstdc++-v3/include/std/spanstream
index 23a340a746e8..7c2ef315e297 100644
--- a/libstdc++-v3/include/std/spanstream
+++ b/libstdc++-v3/include/std/spanstream
@@ -224,7 +224,9 @@ template<typename _CharT, typename _Traits>
   { __x.swap(__y); }
 
 using spanbuf = basic_spanbuf<char>;
+#ifdef _GLIBCXX_USE_WCHAR_T
 using wspanbuf = basic_spanbuf<wchar_t>;
+#endif
 
 template<typename _CharT, typename _Traits>
   class basic_ispanstream
@@ -318,7 +320,9 @@ template<typename _CharT, typename _Traits>
   { __x.swap(__y); }
 
 using ispanstream = basic_ispanstream<char>;
+#ifdef _GLIBCXX_USE_WCHAR_T
 using wispanstream = basic_ispanstream<wchar_t>;
+#endif
 
 template<typename _CharT, typename _Traits>
   class basic_ospanstream
@@ -388,7 +392,9 @@ template<typename _CharT, typename _Traits>
   { __x.swap(__y); }
 
 using ospanstream = basic_ospanstream<char>;
+#ifdef _GLIBCXX_USE_WCHAR_T
 using wospanstream = basic_ospanstream<wchar_t>;
+#endif
 
 template<typename _CharT, typename _Traits>
   class basic_spanstream
@@ -458,7 +464,9 @@ template<typename _CharT, typename _Traits>
   { __x.swap(__y); }
 
 using spanstream = basic_spanstream<char>;
+#ifdef _GLIBCXX_USE_WCHAR_T
 using wspanstream = basic_spanstream<wchar_t>;
+#endif
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
diff --git a/libstdc++-v3/include/std/syncstream b/libstdc++-v3/include/std/syncstream
index e2b5a199ec93..6dfb1367953d 100644
--- a/libstdc++-v3/include/std/syncstream
+++ b/libstdc++-v3/include/std/syncstream
@@ -309,10 +309,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { __x.swap(__y); }
 
   using syncbuf = basic_syncbuf<char>;
-  using wsyncbuf = basic_syncbuf<wchar_t>;
-
   using osyncstream = basic_osyncstream<char>;
+#ifdef _GLIBCXX_USE_WCHAR_T
+  using wsyncbuf = basic_syncbuf<wchar_t>;
   using wosyncstream = basic_osyncstream<wchar_t>;
+#endif
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 #endif // __cpp_lib_syncbuf
diff --git a/libstdc++-v3/src/c++23/std.cc.in b/libstdc++-v3/src/c++23/std.cc.in
index 36e4361e2a3f..fe92986d79f5 100644
--- a/libstdc++-v3/src/c++23/std.cc.in
+++ b/libstdc++-v3/src/c++23/std.cc.in
@@ -1329,17 +1329,19 @@ export namespace std
 #endif
   using std::formatter;
   using std::make_format_args;
-  using std::make_wformat_args;
 #if __cpp_lib_format >= 202311L // >= C++26
   using std::runtime_format;
 #endif
   using std::vformat;
   using std::vformat_to;
   using std::visit_format_arg;
+#ifdef _GLIBCXX_USE_WCHAR_T
+  using std::make_wformat_args;
   using std::wformat_args;
   using std::wformat_context;
   using std::wformat_parse_context;
   using std::wformat_string;
+#endif
 #ifdef __cpp_lib_format_ranges
   using std::format_kind;
   using std::range_format;
@@ -1374,10 +1376,12 @@ export namespace std
   using std::ifstream;
   using std::ofstream;
   using std::swap;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wfilebuf;
   using std::wfstream;
   using std::wifstream;
   using std::wofstream;
+#endif
 }
 
 // <functional>
@@ -1564,7 +1568,9 @@ export namespace std
   using std::streamsize;
   using std::unitbuf;
   using std::uppercase;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wios;
+#endif
 }
 
 // <iosfwd>
@@ -1583,9 +1589,11 @@ export namespace std
   using std::basic_syncbuf;
   using std::osyncstream;
   using std::syncbuf;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wosyncstream;
   using std::wsyncbuf;
 #endif
+#endif
 }
 
 // <iostream>
@@ -1595,10 +1603,12 @@ export namespace std
   using std::cin;
   using std::clog;
   using std::cout;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wcerr;
   using std::wcin;
   using std::wclog;
   using std::wcout;
+#endif
 }
 
 // <istream>
@@ -1608,8 +1618,10 @@ export namespace std
   using std::basic_istream;
   using std::iostream;
   using std::istream;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wiostream;
   using std::wistream;
+#endif
   using std::ws;
   using std::operator>>;
 }
@@ -2116,7 +2128,9 @@ export namespace std
   using std::ends;
   using std::flush;
   using std::ostream;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wostream;
+#endif
   using std::operator<<;
 #ifdef __cpp_lib_syncbuf
   using std::emit_on_flush;
@@ -2537,9 +2551,11 @@ export namespace std
   using std::ssub_match;
   using std::sub_match;
   using std::swap;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wcsub_match;
   using std::wregex;
   using std::wssub_match;
+#endif
   using std::operator==;
   using std::operator<=>;
   using std::operator<<;
@@ -2555,20 +2571,24 @@ export namespace std
   using std::smatch;
   using std::sregex_iterator;
   using std::sregex_token_iterator;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wcmatch;
   using std::wcregex_iterator;
   using std::wcregex_token_iterator;
   using std::wsmatch;
   using std::wsregex_iterator;
   using std::wsregex_token_iterator;
+#endif
   namespace pmr
   {
 #if _GLIBCXX_USE_CXX11_ABI
     using std::pmr::cmatch;
     using std::pmr::match_results;
     using std::pmr::smatch;
+#ifdef _GLIBCXX_USE_WCHAR_T
     using std::pmr::wcmatch;
     using std::pmr::wsmatch;
+#endif
 #endif
   }
 }
@@ -2637,17 +2657,19 @@ export namespace std
 export namespace std
 {
   using std::basic_spanbuf;
-  using std::spanbuf;
-  using std::wspanbuf;
   using std::basic_ispanstream;
-  using std::ispanstream;
-  using std::wispanstream;
   using std::basic_ospanstream;
-  using std::ospanstream;
-  using std::wospanstream;
   using std::basic_spanstream;
+  using std::spanbuf;
+  using std::ispanstream;
+  using std::ospanstream;
   using std::spanstream;
+#ifdef _GLIBCXX_USE_WCHAR_T
+  using std::wspanbuf;
+  using std::wispanstream;
+  using std::wospanstream;
   using std::wspanstream;
+#endif
 }
 #endif
 
@@ -2663,10 +2685,12 @@ export namespace std
   using std::stringbuf;
   using std::stringstream;
   using std::swap;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wistringstream;
   using std::wostringstream;
   using std::wstringbuf;
   using std::wstringstream;
+#endif
 }
 
 // <stack>
@@ -2761,7 +2785,9 @@ export namespace std
 {
   using std::basic_streambuf;
   using std::streambuf;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wstreambuf;
+#endif
 }
 
 // <string>
@@ -2788,7 +2814,9 @@ export namespace std
   using std::stoull;
   using std::string;
   using std::to_string;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::to_wstring;
+#endif
   using std::u16string;
   using std::u32string;
   using std::u8string;
@@ -2853,9 +2881,11 @@ export namespace std
   using std::basic_osyncstream;
   using std::osyncstream;
   using std::syncbuf;
+#ifdef _GLIBCXX_USE_WCHAR_T
   using std::wosyncstream;
   using std::wsyncbuf;
 #endif
+#endif
 }
 
 // 19.5 <system_error>