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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/110149] std::format for pointer arguments allows a
 '0' option
Date: Tue, 06 Jun 2023 22:57:07 +0000
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X-Bugzilla-Component: libstdc++
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110149

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It looks like I forgot to actually format using 'P' though, I only parsed it
from the format string.

This would fix that, and disable the P2519 changes for -std=3Dc++20 and
-std=3Dc++23:

--- a/libstdc++-v3/include/std/format
+++ b/libstdc++-v3/include/std/format
@@ -2081,19 +2081,29 @@ namespace __format
        if (__finished())
          return __first;

+#if __cplusplus > 202302L || ! defined __STRICT_ANSI__
        // _GLIBCXX_RESOLVE_LIB_DEFECTS
        // P2519R3 Formatting pointers
        __first =3D __spec._M_parse_zero_fill(__first, __last);
        if (__finished())
          return __first;
+#endif

        __first =3D __spec._M_parse_width(__first, __last, __pc);

-       if (__first !=3D __last && (*__first =3D=3D 'p' || *__first =3D=3D =
'P'))
+       if (__first !=3D __last)
          {
-           if (*__first =3D=3D 'P')
+           if (*__first =3D=3D 'p')
+             ++__first;
+#if __cplusplus > 202302L || ! defined __STRICT_ANSI__
+           else if (*__first =3D=3D 'P'))
+           {
+             // _GLIBCXX_RESOLVE_LIB_DEFECTS
+             // P2519R3 Formatting pointers
              __spec._M_type =3D __format::_Pres_P;
-           ++__first;
+             ++__first;
+           }
+#endif
          }

        if (__finished())
@@ -2113,6 +2123,18 @@ namespace __format
          const int __n =3D __ptr - __buf;
          __buf[0] =3D '0';
          __buf[1] =3D 'x';
+#if __cplusplus > 202302L || ! defined __STRICT_ANSI__
+         if (_M_spec._M_type =3D=3D _Pres_)
+           {
+             __buf[1] =3D 'X';
+             for (auto __p =3D __buf + 2; __p !=3D __res.ptr; ++__p)
+#if __has_builtin(__builtin_toupper)
+               *__p =3D __builtin_toupper(*__p);
+#else
+               *__p =3D std::toupper(*__p);
+#endif
+           }
+#endif

          basic_string_view<_CharT> __str;
          if constexpr (is_same_v<_CharT, char>)=