[gcc r13-8130] libstdc++: Disable std::formatter::set_debug_format [PR112832]

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

https://gcc.gnu.org/g:d40796e3813fdf646ca7b7ce9630d5cc121353b4

commit r13-8130-gd40796e3813fdf646ca7b7ce9630d5cc121353b4
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Dec 4 12:03:28 2023 +0000

    libstdc++: Disable std::formatter::set_debug_format [PR112832]
    
    All set_debug_format member functions should be guarded by the
    __cpp_lib_formatting_ranges macro (which is not defined yet).
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/112832
            * include/std/format (formatter::set_debug_format): Ensure this
            member is defined conditionally for all specializations.
            * testsuite/std/format/formatter/112832.cc: New test.
    
    (cherry picked from commit 3cd73543a1122d3c81409e3e9a26c3e94c3d324f)

Diff:
---
 libstdc++-v3/include/std/format                    |  8 ++++++
 .../testsuite/std/format/formatter/112832.cc       | 29 ++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format
index 17ebae676e9..a48bb2e161d 100644
--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -1823,9 +1823,11 @@ namespace __format
 	    return _M_f.format(__u, __fc);
 	}
 
+#if __cpp_lib_format_ranges
       constexpr void
       set_debug_format() noexcept
       { _M_f._M_spec._M_type = __format::_Pres_esc; }
+#endif
 
     private:
       __format::__formatter_int<wchar_t> _M_f;
@@ -1850,7 +1852,9 @@ namespace __format
 	format(_CharT* __u, basic_format_context<_Out, _CharT>& __fc) const
 	{ return _M_f.format(__u, __fc); }
 
+#if __cpp_lib_format_ranges
       constexpr void set_debug_format() noexcept { _M_f.set_debug_format(); }
+#endif
 
     private:
       __format::__formatter_str<_CharT> _M_f;
@@ -1873,7 +1877,9 @@ namespace __format
 	       basic_format_context<_Out, _CharT>& __fc) const
 	{ return _M_f.format(__u, __fc); }
 
+#if __cpp_lib_format_ranges
       constexpr void set_debug_format() noexcept { _M_f.set_debug_format(); }
+#endif
 
     private:
       __format::__formatter_str<_CharT> _M_f;
@@ -1895,7 +1901,9 @@ namespace __format
 	       basic_format_context<_Out, _CharT>& __fc) const
 	{ return _M_f.format({__u, _Nm}, __fc); }
 
+#if __cpp_lib_format_ranges
       constexpr void set_debug_format() noexcept { _M_f.set_debug_format(); }
+#endif
 
     private:
       __format::__formatter_str<_CharT> _M_f;
diff --git a/libstdc++-v3/testsuite/std/format/formatter/112832.cc b/libstdc++-v3/testsuite/std/format/formatter/112832.cc
new file mode 100644
index 00000000000..9aa2095a73d
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/format/formatter/112832.cc
@@ -0,0 +1,29 @@
+// { dg-do compile { target c++20 } }
+
+#include <format>
+
+template<typename T,
+	 typename C = std::remove_cvref_t<decltype(std::declval<T&>()[0])>>
+constexpr bool
+test_pr112832()
+{
+  std::formatter<T, C> f;
+  if constexpr (requires{ f.set_debug_format(); })
+    f.set_debug_format();
+  return true;
+}
+
+int main()
+{
+  static_assert(test_pr112832<std::string_view>());
+  static_assert(test_pr112832<char*>());
+  static_assert(test_pr112832<const char*>());
+  static_assert(test_pr112832<char[1]>());
+#ifdef _GLIBCXX_USE_WCHAR_T
+  static_assert(test_pr112832<std::wstring_view>());
+  static_assert(test_pr112832<wchar_t*>());
+  static_assert(test_pr112832<const wchar_t*>());
+  static_assert(test_pr112832<wchar_t[1]>());
+  static_assert(test_pr112832<char, wchar_t>());
+#endif
+}