[gcc r14-5588] libstdc++: Check string value_type in std::make_format_args [PR112607]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:279e407a06cc676d8e6e0bb5755b0a804e05377c

commit r14-5588-g279e407a06cc676d8e6e0bb5755b0a804e05377c
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Sat Nov 18 20:56:35 2023 +0000

    libstdc++: Check string value_type in std::make_format_args [PR112607]
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/112607
            * include/std/format (basic_format_arg::_S_to_arg_type): Check
            value_type for basic_string_view and basic_string
            specializations.
            * testsuite/std/format/arguments/112607.cc: New test.

Diff:
---
 libstdc++-v3/include/std/format                    | 12 ++++++---
 .../testsuite/std/format/arguments/112607.cc       | 30 ++++++++++++++++++++++
 2 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 7c52cce5dbb..58cd310db4d 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -3220,10 +3220,14 @@ namespace __format
 	    return type_identity<__format::__float128_t>();
 # endif
 #endif
-	  else if constexpr (__is_specialization_of<_Td, basic_string_view>)
-	    return type_identity<basic_string_view<_CharT>>();
-	  else if constexpr (__is_specialization_of<_Td, basic_string>)
-	    return type_identity<basic_string_view<_CharT>>();
+	  else if constexpr (__is_specialization_of<_Td, basic_string_view>
+			    || __is_specialization_of<_Td, basic_string>)
+	    {
+	      if constexpr (is_same_v<typename _Td::value_type, _CharT>)
+		return type_identity<basic_string_view<_CharT>>();
+	      else
+		return type_identity<handle>();
+	    }
 	  else if constexpr (is_same_v<decay_t<_Td>, const _CharT*>)
 	    return type_identity<const _CharT*>();
 	  else if constexpr (is_same_v<decay_t<_Td>, _CharT*>)
diff --git a/libstdc++-v3/testsuite/std/format/arguments/112607.cc b/libstdc++-v3/testsuite/std/format/arguments/112607.cc
new file mode 100644
index 00000000000..19eec765ea5
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/format/arguments/112607.cc
@@ -0,0 +1,30 @@
+// { dg-do compile { target c++20 } }
+
+// PR libstdc++/112607
+// _Normalize does not consider char_type for the basic_string_view case
+
+#include <format>
+
+template<typename T>
+struct Alloc
+{
+  using value_type = T;
+  Alloc() = default;
+  template<typename U>
+    Alloc(const Alloc<U>&) { }
+  T* allocate(std::size_t);
+  void deallocate(T*, std::size_t);
+  bool operator==(const Alloc&) const;
+};
+
+template<typename C>
+using String = std::basic_string<C, std::char_traits<C>, Alloc<C>>;
+
+template<>
+struct std::formatter<String<wchar_t>> : std::formatter<std::string> {
+  auto format(const String<wchar_t>&, auto& ctx) const {
+    return std::formatter<std::string>::format(" ", ctx);
+  }
+};
+
+std::string str = std::format("{}", String<wchar_t>{});