On Thu, Nov 02, 2023 at 10:23:27PM -0400, Jason Merrill wrote:
> Under the existing diagnostic I'd like to distinguish the different cases
> more, e.g.
> 
> "multicharacter literal with %d characters exceeds 'int' size of %d bytes"
> "multicharacter literal cannot have an encoding prefix"

Ok.  The following updated patch does all of that.  I've also integrated
the follow-up patch into it (to count the source character set characters
correctly).

I've just used multi-character rather than multicharacter because the
existing diagnostics spell it that way (I know the C++ standard doesn't
use the hyphen).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-11-03  Jakub Jelinek  <ja...@redhat.com>

        PR c++/110341
libcpp/
        * charset.cc: Implement C++ 26 P1854R4 - Making non-encodable string
        literals ill-formed.
        (one_count_chars, convert_count_chars, count_source_chars): New
        functions.
        (narrow_str_to_charconst): Change last arg type from cpp_ttype to
        const cpp_token *.  For C++ if pedantic and i > 1 in CPP_CHAR
        interpret token also as CPP_STRING32 and if number of characters
        in the CPP_STRING32 is larger than number of bytes in CPP_CHAR,
        pedwarn on it.  Make the diagnostics more detailed.
        (wide_str_to_charconst): Change last arg type from cpp_ttype to
        const cpp_token *.  Make the diagnostics more detailed.
        (cpp_interpret_charconst): Adjust narrow_str_to_charconst and
        wide_str_to_charconst callers.
gcc/testsuite/
        * g++.dg/cpp26/literals1.C: New test.
        * g++.dg/cpp26/literals2.C: New test.
        * g++.dg/cpp23/wchar-multi1.C: Adjust expected diagnostic wordings.
        * g++.dg/cpp23/wchar-multi2.C: Likewise.
        * gcc.dg/c2x-utf8char-3.c: Likewise.
        * gcc.dg/cpp/charconst-4.c: Likewise.
        * gcc.dg/cpp/charconst.c: Likewise.
        * gcc.dg/cpp/if-2.c: Likewise.
        * gcc.dg/utf16-4.c: Likewise.
        * gcc.dg/utf32-4.c: Likewise.
        * g++.dg/cpp1z/utf8-neg.C: Likewise.
        * g++.dg/cpp2a/ucn2.C: Likewise.
        * g++.dg/ext/utf16-4.C: Likewise.
        * g++.dg/ext/utf32-4.C: Likewise.

--- libcpp/charset.cc.jj        2023-11-02 07:49:20.975811244 +0100
+++ libcpp/charset.cc   2023-11-03 11:57:56.738701066 +0100
@@ -446,6 +446,73 @@ one_utf16_to_utf8 (iconv_t bigend, const
   return 0;
 }
 
+
+/* Special routine which just counts number of characters in the
+   string, what exactly is stored into the output doesn't matter
+   as long as it is one uchar per character.  */
+
+static inline int
+one_count_chars (iconv_t, const uchar **inbufp, size_t *inbytesleftp,
+                uchar **outbufp, size_t *outbytesleftp)
+{
+  cppchar_t s = 0;
+  int rval;
+
+  /* Check for space first, since we know exactly how much we need.  */
+  if (*outbytesleftp < 1)
+    return E2BIG;
+
+#if HOST_CHARSET == HOST_CHARSET_ASCII
+  rval = one_utf8_to_cppchar (inbufp, inbytesleftp, &s);
+  if (rval)
+    return rval;
+#else
+  if (*inbytesleftp < 1)
+    return EINVAL;
+  static const uchar utf_ebcdic_map[256] = {
+    /* See table 4 in http://unicode.org/reports/tr16/tr16-7.2.html  */
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+    1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 1, 1, 1, 1, 1,
+    1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 1, 1, 1, 1, 1, 1,
+    1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 1, 1, 1, 1, 1,
+    9, 9, 9, 9, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1,
+    2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
+    2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2,
+    2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 2, 2,
+    2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 1, 3, 3,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 3, 3, 3, 3,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 3, 4, 4, 4, 4,
+    1, 4, 1, 1, 1, 1, 1, 1, 1, 1, 4, 4, 4, 5, 5, 5,
+    1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 6, 6, 7, 7, 0
+  };
+  rval = utf_ebcdic_map[**inbufp];
+  if (rval == 9)
+    return EILSEQ;
+  if (rval == 0)
+    rval = 1;
+  if (rval >= 2)
+    {
+      if (*inbytesleftp < rval)
+       return EINVAL;
+      for (int i = 1; i < rval; ++i)
+       if (utf_ebcdic_map[(*inbufp)[i]] != 9)
+         return EILSEQ;
+    }
+  *inbytesleftp -= rval;
+  *inbufp += rval;
+#endif
+
+  **outbufp = ' ';
+
+  *outbufp += 1;
+  *outbytesleftp -= 1;
+  return 0;
+}
+
+
 /* Helper routine for the next few functions.  The 'const' on
    one_conversion means that we promise not to modify what function is
    pointed to, which lets the inliner see through it.  */
@@ -529,6 +596,15 @@ convert_utf32_utf8 (iconv_t cd, const uc
   return conversion_loop (one_utf32_to_utf8, cd, from, flen, to);
 }
 
+/* Magic conversion which just counts characters from input, so
+   only to->len is significant.  */
+static bool
+convert_count_chars (iconv_t cd, const uchar *from,
+                    size_t flen, struct _cpp_strbuf *to)
+{
+  return conversion_loop (one_count_chars, cd, from, flen, to);
+}
+
 /* Identity conversion, used when we have no alternative.  */
 static bool
 convert_no_conversion (iconv_t cd ATTRIBUTE_UNUSED,
@@ -2574,21 +2650,49 @@ cpp_interpret_string_notranslate (cpp_re
 }
 
 
+/* Return number of source characters in STR.  */
+static unsigned
+count_source_chars (cpp_reader *pfile, cpp_string str, cpp_ttype type)
+{
+  cpp_string str2 = { 0, 0 };
+  bool (*saved_diagnostic_handler) (cpp_reader *, enum cpp_diagnostic_level,
+                                   enum cpp_warning_reason, rich_location *,
+                                   const char *, va_list *)
+    ATTRIBUTE_FPTR_PRINTF(5,0);
+  saved_diagnostic_handler = pfile->cb.diagnostic;
+  pfile->cb.diagnostic = noop_diagnostic_cb;
+  convert_f save_func = pfile->narrow_cset_desc.func;
+  pfile->narrow_cset_desc.func = convert_count_chars;
+  bool ret = cpp_interpret_string (pfile, &str, 1, &str2, type);
+  pfile->narrow_cset_desc.func = save_func;
+  pfile->cb.diagnostic = saved_diagnostic_handler;
+  if (ret)
+    {
+      if (str2.text != str.text)
+       free ((void *)str2.text);
+      return str2.len;
+    }
+  else
+    return 0;
+}
+
 /* Subroutine of cpp_interpret_charconst which performs the conversion
    to a number, for narrow strings.  STR is the string structure returned
    by cpp_interpret_string.  PCHARS_SEEN and UNSIGNEDP are as for
-   cpp_interpret_charconst.  TYPE is the token type.  */
+   cpp_interpret_charconst.  TOKEN is the token.  */
 static cppchar_t
 narrow_str_to_charconst (cpp_reader *pfile, cpp_string str,
                         unsigned int *pchars_seen, int *unsignedp,
-                        enum cpp_ttype type)
+                        const cpp_token *token)
 {
+  enum cpp_ttype type = token->type;
   size_t width = CPP_OPTION (pfile, char_precision);
   size_t max_chars = CPP_OPTION (pfile, int_precision) / width;
   size_t mask = width_to_mask (width);
   size_t i;
   cppchar_t result, c;
   bool unsigned_p;
+  bool diagnosed = false;
 
   /* The value of a multi-character character constant, or a
      single-character character constant whose representation in the
@@ -2612,11 +2716,55 @@ narrow_str_to_charconst (cpp_reader *pfi
 
   if (type == CPP_UTF8CHAR)
     max_chars = 1;
-  if (i > max_chars)
+  else if (i > 1 && CPP_OPTION (pfile, cplusplus) && CPP_PEDANTIC (pfile))
     {
+      /* C++ as a DR since
+        P1854R4 - Making non-encodable string literals ill-formed
+        makes multi-character narrow character literals if any of the
+        characters in the literal isn't encodable in char/unsigned char
+        ill-formed.  We need to count the number of c-chars and compare
+        that to str.len.  */
+      unsigned src_chars = count_source_chars (pfile, token->val.str, type);
+
+      if (src_chars)
+       {
+         if (str.len > src_chars)
+           {
+             if (src_chars <= 2)
+               diagnosed
+                 = cpp_error (pfile, CPP_DL_PEDWARN,
+                              "character not encodable in a single execution "
+                              "character code unit");
+             else
+               diagnosed
+                 = cpp_error (pfile, CPP_DL_PEDWARN,
+                              "at least one character in a multi-character "
+                              "literal not encodable in a single execution "
+                              "character code unit");
+             if (diagnosed && i > max_chars)
+               i = max_chars;
+           }
+       }
+    }
+  if (diagnosed)
+    /* Already diagnosed above.  */;
+  else if (i > max_chars)
+    {
+      unsigned src_chars
+       = count_source_chars (pfile, token->val.str,
+                             type == CPP_UTF8CHAR ? CPP_CHAR : type);
+
+      if (type != CPP_UTF8CHAR)
+       cpp_error (pfile, CPP_DL_WARNING,
+                  "multi-character literal with %ld characters exceeds "
+                  "'int' size of %ld bytes", (long) i, (long) max_chars);
+      else if (src_chars > 2)
+       cpp_error (pfile, CPP_DL_ERROR,
+                  "multi-character literal cannot have an encoding prefix");
+      else
+       cpp_error (pfile, CPP_DL_ERROR,
+                  "character not encodable in a single code unit");
       i = max_chars;
-      cpp_error (pfile, type == CPP_UTF8CHAR ? CPP_DL_ERROR : CPP_DL_WARNING,
-                "character constant too long for its type");
     }
   else if (i > 1 && CPP_OPTION (pfile, warn_multichar))
     cpp_warning (pfile, CPP_W_MULTICHAR, "multi-character character constant");
@@ -2651,12 +2799,13 @@ narrow_str_to_charconst (cpp_reader *pfi
 /* Subroutine of cpp_interpret_charconst which performs the conversion
    to a number, for wide strings.  STR is the string structure returned
    by cpp_interpret_string.  PCHARS_SEEN and UNSIGNEDP are as for
-   cpp_interpret_charconst.  TYPE is the token type.  */
+   cpp_interpret_charconst.  TOKEN is the token.  */
 static cppchar_t
 wide_str_to_charconst (cpp_reader *pfile, cpp_string str,
                       unsigned int *pchars_seen, int *unsignedp,
-                      enum cpp_ttype type)
+                      const cpp_token *token)
 {
+  enum cpp_ttype type = token->type;
   bool bigend = CPP_OPTION (pfile, bytes_big_endian);
   size_t width = converter_for_type (pfile, type).width;
   size_t cwidth = CPP_OPTION (pfile, char_precision);
@@ -2692,14 +2841,25 @@ wide_str_to_charconst (cpp_reader *pfile
      character exactly fills a wchar_t, so a multi-character wide
      character constant is guaranteed to overflow.  */
   if (str.len > nbwc * 2)
-    cpp_error (pfile, (CPP_OPTION (pfile, cplusplus)
-                      && (type == CPP_CHAR16
-                          || type == CPP_CHAR32
-                          /* In C++23 this is error even for L'ab'.  */
-                          || (type == CPP_WCHAR
-                              && CPP_OPTION (pfile, size_t_literals))))
-                     ? CPP_DL_ERROR : CPP_DL_WARNING,
-              "character constant too long for its type");
+    {
+      cpp_diagnostic_level level = CPP_DL_WARNING;
+      unsigned src_chars
+       = count_source_chars (pfile, token->val.str, CPP_CHAR);
+
+      if (CPP_OPTION (pfile, cplusplus)
+         && (type == CPP_CHAR16
+             || type == CPP_CHAR32
+             /* In C++23 this is error even for L'ab'.  */
+             || (type == CPP_WCHAR
+                 && CPP_OPTION (pfile, size_t_literals))))
+       level = CPP_DL_ERROR;
+      if (src_chars > 2)
+       cpp_error (pfile, level,
+                  "multi-character literal cannot have an encoding prefix");
+      else
+       cpp_error (pfile, level,
+                  "character not encodable in a single code unit");
+    }
 
   /* Truncate the constant to its natural width, and simultaneously
      sign- or zero-extend to the full width of cppchar_t.  */
@@ -2754,10 +2914,10 @@ cpp_interpret_charconst (cpp_reader *pfi
 
   if (wide)
     result = wide_str_to_charconst (pfile, str, pchars_seen, unsignedp,
-                                   token->type);
+                                   token);
   else
     result = narrow_str_to_charconst (pfile, str, pchars_seen, unsignedp,
-                                     token->type);
+                                     token);
 
   if (str.text != token->val.str.text)
     free ((void *)str.text);
--- gcc/testsuite/g++.dg/cpp23/wchar-multi1.C.jj        2022-08-26 
16:06:10.578493272 +0200
+++ gcc/testsuite/g++.dg/cpp23/wchar-multi1.C   2023-11-03 12:03:38.982933997 
+0100
@@ -4,18 +4,19 @@
 
 char a = 'a';
 int b = 'ab';                  // { dg-warning "multi-character character 
constant" }
-int c = '\u05D9';              // { dg-warning "multi-character character 
constant" }
+int c = '\u05D9';              // { dg-error "character not encodable in a 
single execution character code unit" }
 #if __SIZEOF_INT__ > 2
-int d = '\U0001F525';          // { dg-warning "multi-character character 
constant" "" { target int32 } }
+int d = '\U0001F525';          // { dg-error "character not encodable in a 
single execution character code unit" "" { target int32 } }
 #endif
-int e = 'abcd';                        // { dg-warning "multi-character 
character constant" }
+int e = 'abcd';                        // { dg-warning "multi-character 
character constant" "" { target int32plus } }
+                               // { dg-warning "multi-character literal with 
\[0-9]+ characters exceeds 'int' size of \[0-9]+ bytes" "" { target { ! 
int32plus } } .-1 }
 wchar_t f = L'f';
-wchar_t g = L'gh';             // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t h = L'ijkl';           // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t i = L'\U0001F525';     // { dg-error "character constant too long for 
its type" "" { target { c++23 && { ! 4byte_wchar_t } } } }
-                               // { dg-warning "character constant too long 
for its type" "" { target { c++20_down && { ! 4byte_wchar_t } } } .-1 }
+wchar_t g = L'gh';             // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t h = L'ijkl';           // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t i = L'\U0001F525';     // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target { c++23 && { ! 4byte_wchar_t } } } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target { c++20_down && { ! 4byte_wchar_t } } } 
.-1 }
 #ifdef __cpp_char8_t
 typedef char8_t u8;
 #else
@@ -23,20 +24,20 @@ typedef char u8;
 #endif
 #if __cpp_unicode_characters >= 201411 
 u8 j = u8'j';
-u8 k = u8'kl';                 // { dg-error "character constant too long for 
its type" "" { target c++17 } }
-u8 l = u8'\U0001F525';         // { dg-error "character constant too long for 
its type" "" { target c++17 }  }
+u8 k = u8'kl';                 // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++17 } }
+u8 l = u8'\U0001F525';         // { dg-error "character not encodable in a 
single code unit" "" { target c++17 }  }
 #endif
 #if __cpp_unicode_characters >= 200704
 char16_t m = u'm';
-char16_t n = u'no';            // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char16_t n = u'no';            // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++11 } }
 char16_t o = u'\u05D9';
-char16_t p = u'\U0001F525';    // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char16_t p = u'\U0001F525';    // { dg-error "character not encodable in a 
single code unit" "" { target c++11 } }
 char32_t q = U'm';
-char32_t r = U'no';            // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char32_t r = U'no';            // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++11 } }
 char32_t s = U'\u05D9';
 char32_t t = U'\U0001F525';
 #endif
-wchar_t u = L'\u0065\u0301';           // { dg-error "character constant too 
long for its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t v = L'é';             // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
+wchar_t u = L'\u0065\u0301';           // { dg-error "multi-character literal 
cannot have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t v = L'é';             // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
--- gcc/testsuite/g++.dg/cpp23/wchar-multi2.C.jj        2022-08-26 
16:06:10.578493272 +0200
+++ gcc/testsuite/g++.dg/cpp23/wchar-multi2.C   2023-11-03 12:06:44.661347711 
+0100
@@ -11,12 +11,12 @@ int d = '\U0001F525';               // { dg-warning "
 #endif
 int e = 'abcd';                        // { dg-warning "multi-character 
character constant" }
 wchar_t f = L'f';
-wchar_t g = L'gh';             // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t h = L'ijkl';           // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t i = L'\U0001F525';     // { dg-error "character constant too long for 
its type" "" { target { c++23 } } }
-                               // { dg-warning "character constant too long 
for its type" "" { target { c++20_down } } .-1 }
+wchar_t g = L'gh';             // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t h = L'ijkl';           // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t i = L'\U0001F525';     // { dg-error "character not encodable in a 
single code unit" "" { target { c++23 } } }
+                               // { dg-warning "character not encodable in a 
single code unit" "" { target { c++20_down } } .-1 }
 #ifdef __cpp_char8_t
 typedef char8_t u8;
 #else
@@ -24,20 +24,20 @@ typedef char u8;
 #endif
 #if __cpp_unicode_characters >= 201411 
 u8 j = u8'j';
-u8 k = u8'kl';                 // { dg-error "character constant too long for 
its type" "" { target c++17 } }
-u8 l = u8'\U0001F525';         // { dg-error "character constant too long for 
its type" "" { target c++17 }  }
+u8 k = u8'kl';                 // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++17 } }
+u8 l = u8'\U0001F525';         // { dg-error "character not encodable in a 
single code unit" "" { target c++17 }  }
 #endif
 #if __cpp_unicode_characters >= 200704
 char16_t m = u'm';
-char16_t n = u'no';            // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char16_t n = u'no';            // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++11 } }
 char16_t o = u'\u05D9';
-char16_t p = u'\U0001F525';    // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char16_t p = u'\U0001F525';    // { dg-error "character not encodable in a 
single code unit" "" { target c++11 } }
 char32_t q = U'm';
-char32_t r = U'no';            // { dg-error "character constant too long for 
its type" "" { target c++11 } }
+char32_t r = U'no';            // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++11 } }
 char32_t s = U'\u05D9';
 char32_t t = U'\U0001F525';
 #endif
-wchar_t u = L'\u0065\u0301';           // { dg-error "character constant too 
long for its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
-wchar_t v = L'é';             // { dg-error "character constant too long for 
its type" "" { target c++23 } }
-                               // { dg-warning "character constant too long 
for its type" "" { target c++20_down } .-1 }
+wchar_t u = L'\u0065\u0301';           // { dg-error "multi-character literal 
cannot have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
+wchar_t v = L'é';             // { dg-error "multi-character literal cannot 
have an encoding prefix" "" { target c++23 } }
+                               // { dg-warning "multi-character literal cannot 
have an encoding prefix" "" { target c++20_down } .-1 }
--- gcc/testsuite/g++.dg/cpp26/literals1.C.jj   2023-11-03 09:56:28.103335149 
+0100
+++ gcc/testsuite/g++.dg/cpp26/literals1.C      2023-11-03 12:43:05.043977373 
+0100
@@ -0,0 +1,66 @@
+// C++26 P1854R4 - Making non-encodable string literals ill-formed
+// { dg-do compile { target c++11 } }
+// { dg-require-effective-target int32 }
+// { dg-options "-pedantic-errors -finput-charset=UTF-8 -fexec-charset=UTF-8" }
+
+int a = 'abcd';                                                // { dg-warning 
"multi-character character constant" }
+int b = '\x61\x62\x63\x64';                            // { dg-warning 
"multi-character character constant" }
+int c = 'á';                                           // { dg-error 
"character not encodable in a single execution character code unit" }
+int d = '😁';                                           // { dg-error 
"character not encodable in a single execution character code unit" }
+int e = '\N{FACE WITH TEARS OF JOY}';                  // { dg-error 
"character not encodable in a single execution character code unit" }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } .-1 }
+int f = '\U0001F602';                                  // { dg-error 
"character not encodable in a single execution character code unit" }
+wchar_t g = L'abcd';                                   // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++23 } }
+                                                       // { dg-warning 
"multi-character literal cannot have an encoding prefix" "" { target c++20_down 
} .-1 }
+wchar_t h = L'\x61\x62\x63\x64';                       // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++23 } }
+                                                       // { dg-warning 
"multi-character literal cannot have an encoding prefix" "" { target c++20_down 
} .-1 }
+wchar_t i = L'á';
+char16_t j = u'abcd';                                  // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char16_t k = u'\x61\x62\x63\x64';                      // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char16_t l = u'á';
+char16_t m = u'😁';                                     // { dg-error 
"character not encodable in a single code unit" }
+char16_t n = u'\N{FACE WITH TEARS OF JOY}';            // { dg-error 
"character not encodable in a single code unit" { target c++23 } }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } .-1 }
+char16_t o = u'\U0001F602';                            // { dg-error 
"character not encodable in a single code unit" }
+char32_t p = U'abcd';                                  // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char32_t q = U'\x61\x62\x63\x64';                      // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char32_t r = U'á';
+char32_t s = U'😁';
+char32_t t = U'\N{FACE WITH TEARS OF JOY}';            // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+char32_t u = U'\U0001F602';
+#if __cpp_unicode_characters >= 201411L
+auto v = u8'abcd';                                     // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++17 } }
+auto w = u8'\x61\x62\x63\x64';                         // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++17 } }
+auto x = u8'á';                                                // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+auto y = u8'😁';                                        // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+auto z = u8'\N{FACE WITH TEARS OF JOY}';               // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target { c++17 && 
c++20_down } } .-1 }
+auto aa = u8'\U0001F602';                              // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+#endif
+const char *ab = "😁";
+const char *ac = "\N{FACE WITH TEARS OF JOY}";         // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+const char *ad = "\U0001F602";
+const char16_t *ae = u"😁";
+const char16_t *af = u"\N{FACE WITH TEARS OF JOY}";    // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+const char16_t *ag = u"\U0001F602";
+const char32_t *ah = U"😁";
+const char32_t *ai = U"\N{FACE WITH TEARS OF JOY}";    // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+const char32_t *aj = U"\U0001F602";
+auto ak = u8"😁";
+auto al = u8"\N{FACE WITH TEARS OF JOY}";              // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+auto am = u8"\U0001F602";
+int an = '\x123456789';                                        // { dg-error 
"hex escape sequence out of range" }
+wchar_t ao = L'\x123456789abcdef0';                    // { dg-error "hex 
escape sequence out of range" }
+char16_t ap = u'\x12345678';                           // { dg-error "hex 
escape sequence out of range" }
+char32_t aq = U'\x123456789abcdef0';                   // { dg-error "hex 
escape sequence out of range" }
+#if __cpp_unicode_characters >= 201411L
+auto ar = u8'\x123456789abcdef0';                      // { dg-error "hex 
escape sequence out of range" "" { target c++17 } }
+#endif
+char as = '\xff';
+#if __SIZEOF_WCHAR_T__ * __CHAR_BIT__ == 32
+wchar_t at = L'\xffffffff';
+#elif __SIZEOF_WCHAR_T__ * __CHAR_BIT__ == 16
+wchar_t at = L'\xffff';
+#endif
+int au = '\x1234';                                     // { dg-error "hex 
escape sequence out of range" }
+int av = 'abcdefghijklmnop';                           // { dg-warning 
"multi-character literal with \[0-9]+ characters exceeds 'int' size of \[0-9]+ 
bytes" }
--- gcc/testsuite/g++.dg/cpp26/literals2.C.jj   2023-11-03 09:56:28.108335079 
+0100
+++ gcc/testsuite/g++.dg/cpp26/literals2.C      2023-11-03 12:44:02.932171027 
+0100
@@ -0,0 +1,68 @@
+// C++26 P1854R4 - Making non-encodable string literals ill-formed
+// { dg-do compile { target c++11 } }
+// { dg-require-effective-target int32 }
+// { dg-options "-pedantic-errors -finput-charset=UTF-8 
-fexec-charset=ISO-8859-1" }
+/* { dg-require-iconv "ISO-8859-1" } */
+
+int a = 'abcd';                                                // { dg-warning 
"multi-character character constant" }
+int b = '\x61\x62\x63\x64';                            // { dg-warning 
"multi-character character constant" }
+int c = 'á';
+int d = '😁';                                           // { dg-error 
"converting to execution character set" }
+int e = '\N{FACE WITH TEARS OF JOY}';                  // { dg-error 
"converting UCN to execution character set" }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } .-1 }
+int f = '\U0001F602';                                  // { dg-error 
"converting UCN to execution character set" }
+wchar_t g = L'abcd';                                   // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++23 } }
+                                                       // { dg-warning 
"multi-character literal cannot have an encoding prefix" "" { target c++20_down 
} .-1 }
+wchar_t h = L'\x61\x62\x63\x64';                       // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++23 } }
+                                                       // { dg-warning 
"multi-character literal cannot have an encoding prefix" "" { target c++20_down 
} .-1 }
+wchar_t i = L'á';
+char16_t j = u'abcd';                                  // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char16_t k = u'\x61\x62\x63\x64';                      // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char16_t l = u'á';
+char16_t m = u'😁';                                     // { dg-error 
"character not encodable in a single code unit" }
+char16_t n = u'\N{FACE WITH TEARS OF JOY}';            // { dg-error 
"character not encodable in a single code unit" { target c++23 } }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } .-1 }
+char16_t o = u'\U0001F602';                            // { dg-error 
"character not encodable in a single code unit" }
+char32_t p = U'abcd';                                  // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char32_t q = U'\x61\x62\x63\x64';                      // { dg-error 
"multi-character literal cannot have an encoding prefix" }
+char32_t r = U'á';
+char32_t s = U'😁';
+char32_t t = U'\N{FACE WITH TEARS OF JOY}';            // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+char32_t u = U'\U0001F602';
+#if __cpp_unicode_characters >= 201411L
+auto v = u8'abcd';                                     // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++17 } }
+auto w = u8'\x61\x62\x63\x64';                         // { dg-error 
"multi-character literal cannot have an encoding prefix" "" { target c++17 } }
+auto x = u8'á';                                                // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+auto y = u8'😁';                                        // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+auto z = u8'\N{FACE WITH TEARS OF JOY}';               // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target { c++17 && 
c++20_down } } .-1 }
+auto aa = u8'\U0001F602';                              // { dg-error 
"character not encodable in a single code unit" "" { target c++17 } }
+#endif
+const char *ab = "😁";                                  // { dg-error 
"converting to execution character set" }
+const char *ac = "\N{FACE WITH TEARS OF JOY}";         // { dg-error 
"converting UCN to execution character set" }
+                                                       // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } .-1 }
+const char *ad = "\U0001F602";                         // { dg-error 
"converting UCN to execution character set" }
+const char16_t *ae = u"😁";
+const char16_t *af = u"\N{FACE WITH TEARS OF JOY}";    // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+const char16_t *ag = u"\U0001F602";
+const char32_t *ah = U"😁";
+const char32_t *ai = U"\N{FACE WITH TEARS OF JOY}";    // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+const char32_t *aj = U"\U0001F602";
+auto ak = u8"😁";
+auto al = u8"\N{FACE WITH TEARS OF JOY}";              // { dg-error "named 
universal character escapes are only valid in" "" { target c++20_down } }
+auto am = u8"\U0001F602";
+int an = '\x123456789';                                        // { dg-error 
"hex escape sequence out of range" }
+wchar_t ao = L'\x123456789abcdef0';                    // { dg-error "hex 
escape sequence out of range" }
+char16_t ap = u'\x12345678';                           // { dg-error "hex 
escape sequence out of range" }
+char32_t aq = U'\x123456789abcdef0';                   // { dg-error "hex 
escape sequence out of range" }
+#if __cpp_unicode_characters >= 201411L
+auto ar = u8'\x123456789abcdef0';                      // { dg-error "hex 
escape sequence out of range" "" { target c++17 } }
+#endif
+char as = '\xff';
+#if __SIZEOF_WCHAR_T__ * __CHAR_BIT__ == 32
+wchar_t at = L'\xffffffff';
+#elif __SIZEOF_WCHAR_T__ * __CHAR_BIT__ == 16
+wchar_t at = L'\xffff';
+#endif
+int au = '\x1234';                                     // { dg-error "hex 
escape sequence out of range" }
+int av = 'abcdefghijklmnop';                           // { dg-warning 
"multi-character literal with \[0-9]+ characters exceeds 'int' size of \[0-9]+ 
bytes" }
--- gcc/testsuite/gcc.dg/c2x-utf8char-3.c.jj    2020-01-14 20:02:47.234603078 
+0100
+++ gcc/testsuite/gcc.dg/c2x-utf8char-3.c       2023-11-03 16:43:32.965924076 
+0100
@@ -3,6 +3,6 @@
 /* { dg-options "-std=c2x -pedantic-errors" } */
 
 unsigned char a = u8''; /* { dg-error "empty character constant" } */
-unsigned char b = u8'ab'; /* { dg-error "character constant too long for its 
type" } */
-unsigned char c = u8'\u00ff'; /* { dg-error "character constant too long for 
its type" } */
+unsigned char b = u8'ab'; /* { dg-error "multi-character literal cannot have 
an encoding prefix" } */
+unsigned char c = u8'\u00ff'; /* { dg-error "character not encodable in a 
single code unit" } */
 unsigned char d = u8'\x100'; /* { dg-error "hex escape sequence out of range" 
} */
--- gcc/testsuite/gcc.dg/cpp/charconst-4.c.jj   2020-01-14 20:02:47.252602809 
+0100
+++ gcc/testsuite/gcc.dg/cpp/charconst-4.c      2023-11-03 16:40:43.060203232 
+0100
@@ -38,7 +38,7 @@ extern void abort (void);
 # error Charconst incorrectly sign-extended
 #endif
 
-#if LONG_CHARCONST != SHORT_CHARCONST /* { dg-warning "too long" } */
+#if LONG_CHARCONST != SHORT_CHARCONST /* { dg-warning "multi-character literal 
with \[0-9]+ characters exceeds 'int' size of \[0-9]+ bytes" } */
 # error Overly long charconst truncates wrongly for preprocessor
 #endif
 
@@ -46,7 +46,7 @@ int main ()
 {
   if (POS_CHARCONST < 0)
     abort ();
-  if (LONG_CHARCONST != SHORT_CHARCONST)  /* { dg-warning "too long" } */
+  if (LONG_CHARCONST != SHORT_CHARCONST)  /* { dg-warning "multi-character 
literal with \[0-9]+ characters exceeds 'int' size of \[0-9]+ bytes" } */
     abort ();
   return 0;
 }
--- gcc/testsuite/gcc.dg/cpp/charconst.c.jj     2020-01-14 20:02:47.252602809 
+0100
+++ gcc/testsuite/gcc.dg/cpp/charconst.c        2023-11-03 16:42:02.911132097 
+0100
@@ -11,9 +11,9 @@
 #endif
 #if L''                        /* { dg-error "empty" "empty wide charconst" } 
*/
 #endif
-#if 'very long'                /* { dg-warning "too long" "long charconst" } */
+#if 'very long'                /* { dg-warning "multi-character literal with 
\[0-9]+ characters exceeds 'int' size of \[0-9]+ bytes" "long charconst" } */
 #endif
-#if L'very long'       /* { dg-warning "too long" "long wide charconst" } */
+#if L'very long'       /* { dg-warning "multi-character literal cannot have an 
encoding prefix" "long wide charconst" } */
 #endif
 /* Don't do this test for L'ab'; it depends upon sizeof (wchar_t).  */
 #if 'ab'               /* { dg-warning "multi-char" "multi-character" } */
@@ -27,10 +27,10 @@ void foo ()
   c = '';              /* { dg-error "empty" "empty charconst" } */
   w = L'';             /* { dg-error "empty" "empty wide charconst" } */
 
-  c = 'very long';     /* { dg-warning "too long" "long charconst" } */
-  w = L'very long';    /* { dg-warning "too long" "long wide charconst" } */
+  c = 'very long';     /* { dg-warning "multi-character literal with \[0-9]+ 
characters exceeds 'int' size of \[0-9]+ bytes" "long charconst" } */
+  w = L'very long';    /* { dg-warning "multi-character literal cannot have an 
encoding prefix" "long wide charconst" } */
 
   c = 'ab';            /* { dg-warning "multi-char" "multi-char" } */
   /* Wide charconsts cannot contain more than one wide character.  */
-  w = L'ab';           /* { dg-warning "too long" "multi-char wide" } */
+  w = L'ab';           /* { dg-warning "multi-character literal cannot have an 
encoding prefix" "multi-char wide" } */
 }
--- gcc/testsuite/gcc.dg/cpp/if-2.c.jj  2020-01-14 20:02:47.255602764 +0100
+++ gcc/testsuite/gcc.dg/cpp/if-2.c     2023-11-03 16:39:22.105289183 +0100
@@ -21,7 +21,7 @@
 #if 'abcd' /* { dg-warning "(multi-character character constant)|(character 
constant (is )?too long)" "multi-character charconst" } */
 #endif
 
-#if 'abcdefghi' /* { dg-warning "character constant (is )?too long" "charconst 
too long" } */
+#if 'abcdefghi' /* { dg-warning "multi-character literal with \[0-9]+ 
characters exceeds 'int' size of \[0-9]+ bytes" } */
 #endif
 
 #if '' /* { dg-error "empty character constant" "empty charconst" } */
--- gcc/testsuite/gcc.dg/utf16-4.c.jj   2020-01-14 20:02:47.499599109 +0100
+++ gcc/testsuite/gcc.dg/utf16-4.c      2023-11-03 16:55:43.102129866 +0100
@@ -6,8 +6,8 @@
 typedef __CHAR16_TYPE__ char16_t;
 
 char16_t       c0 = u'';               /* { dg-error "empty character" } */
-char16_t       c1 = u'ab';             /* { dg-warning "constant too long" } */
-char16_t       c2 = u'\U00064321';     /* { dg-warning "constant too long" } */
+char16_t       c1 = u'ab';             /* { dg-warning "multi-character 
literal cannot have an encoding prefix" } */
+char16_t       c2 = u'\U00064321';     /* { dg-warning "character not 
encodable in a single code unit" } */
 
 char16_t       c3 = 'a';
 char16_t       c4 = U'a';
@@ -16,6 +16,6 @@ char16_t      c6 = U'\U00064321';     /* { dg-war
 char16_t       c7 = L'a';
 char16_t       c8 = L'\u2029';
 char16_t       c9 = L'\U00064321';     /* { dg-warning "conversion" "" { 
target { 4byte_wchar_t } } } */
-                                       /* { dg-warning "constant too long" "" 
{ target { ! 4byte_wchar_t } } .-1 } */
+                                       /* { dg-warning "character not 
encodable in a single code unit" "" { target { ! 4byte_wchar_t } } .-1 } */
 
 int main () {}
--- gcc/testsuite/gcc.dg/utf32-4.c.jj   2020-01-14 20:02:47.500599094 +0100
+++ gcc/testsuite/gcc.dg/utf32-4.c      2023-11-03 16:45:33.625305532 +0100
@@ -6,15 +6,15 @@
 typedef __CHAR32_TYPE__ char32_t;
 
 char32_t       c0 = U'';               /* { dg-error "empty character" } */
-char32_t       c1 = U'ab';             /* { dg-warning "constant too long" } */
+char32_t       c1 = U'ab';             /* { dg-warning "multi-character 
literal cannot have an encoding prefix" } */
 char32_t       c2 = U'\U00064321';
 
 char32_t       c3 = 'a';
 char32_t       c4 = u'a';
 char32_t       c5 = u'\u2029';
-char32_t       c6 = u'\U00064321';     /* { dg-warning "constant too long" } */
+char32_t       c6 = u'\U00064321';     /* { dg-warning "character not 
encodable in a single code unit" } */
 char32_t       c7 = L'a';
 char32_t       c8 = L'\u2029';
-char32_t       c9 = L'\U00064321';     /* { dg-warning "constant too long" "" 
{ target { ! 4byte_wchar_t } } } */
+char32_t       c9 = L'\U00064321';     /* { dg-warning "character not 
encodable in a single code unit" "" { target { ! 4byte_wchar_t } } } */
 
 int main () {}
--- gcc/testsuite/g++.dg/cpp1z/utf8-neg.C.jj    2020-01-14 20:02:46.792609699 
+0100
+++ gcc/testsuite/g++.dg/cpp1z/utf8-neg.C       2023-11-03 16:48:25.384001519 
+0100
@@ -1,6 +1,6 @@
 /* { dg-do compile { target c++17 } } */
 
 const static char c0 = u8'';           // { dg-error "empty character" }
-const static char c1 = u8'ab';         // { dg-error "character constant too 
long for its type" }
-const static char c2 = u8'\u0124';     // { dg-error "character constant too 
long for its type" }
-const static char c3 = u8'\U00064321';  // { dg-error "character constant too 
long for its type" }
+const static char c1 = u8'ab';         // { dg-error "multi-character literal 
cannot have an encoding prefix" }
+const static char c2 = u8'\u0124';     // { dg-error "character not encodable 
in a single code unit" }
+const static char c3 = u8'\U00064321';  // { dg-error "character not encodable 
in a single code unit" }
--- gcc/testsuite/g++.dg/cpp2a/ucn2.C.jj        2020-05-13 21:38:28.363420230 
+0200
+++ gcc/testsuite/g++.dg/cpp2a/ucn2.C   2023-11-03 16:50:23.872412086 +0100
@@ -12,18 +12,18 @@ const char32_t *f = U"\uD802";              // { dg-
 const char32_t *g = U"\U0000DFF0";     // { dg-error "is not a valid universal 
character" }
 const char32_t *h = U"\U00110001";     // { dg-error "is outside the UCS 
codespace" "" { target c++20 } }
 #if __cpp_unicode_characters >= 201411
-const char8_t i = u8'\u00C0';          // { dg-error "character constant too 
long for its type" "" { target c++17 } }
+const char8_t i = u8'\u00C0';          // { dg-error "character not encodable 
in a single code unit" "" { target c++17 } }
 #endif
-const char16_t j = u'\U0001F914';      // { dg-error "character constant too 
long for its type" }
+const char16_t j = u'\U0001F914';      // { dg-error "character not encodable 
in a single code unit" }
 const char32_t k = U'\U0001F914';
 #if __cpp_unicode_characters >= 201411
-const char8_t l = u8'ab';              // { dg-error "character constant too 
long for its type" "" { target c++17 } }
+const char8_t l = u8'ab';              // { dg-error "multi-character literal 
cannot have an encoding prefix" "" { target c++17 } }
 #endif
-const char16_t m = u'ab';              // { dg-error "character constant too 
long for its type" }
-const char32_t n = U'ab';              // { dg-error "character constant too 
long for its type" }
+const char16_t m = u'ab';              // { dg-error "multi-character literal 
cannot have an encoding prefix" }
+const char32_t n = U'ab';              // { dg-error "multi-character literal 
cannot have an encoding prefix" }
 #if __cpp_unicode_characters >= 201411
 const char8_t o = u8'\U00110002';      // { dg-error "is outside the UCS 
codespace" "" { target c++20 } }
-                                       // { dg-error "character constant too 
long for its type" "" { target c++17 } .-1 }
+                                       // { dg-error "character not encodable 
in a single code unit" "" { target c++17 } .-1 }
 #endif
 const char16_t p = u'\U00110003';      // { dg-error "is outside the UCS 
codespace" "" { target c++20 } }
                                        // { dg-error "converting UCN to 
execution character set" "" { target *-*-* } .-1 }
--- gcc/testsuite/g++.dg/ext/utf16-4.C.jj       2020-01-14 20:02:46.841608965 
+0100
+++ gcc/testsuite/g++.dg/ext/utf16-4.C  2023-11-03 16:58:51.134607555 +0100
@@ -4,8 +4,8 @@
 
 
 const static char16_t  c0 = u'';               /* { dg-error "empty character" 
} */
-const static char16_t  c1 = u'ab';             /* { dg-error "constant too 
long" } */
-const static char16_t  c2 = u'\U00064321';     /* { dg-error "constant too 
long" } */
+const static char16_t  c1 = u'ab';             /* { dg-error "multi-character 
literal cannot have an encoding prefix" } */
+const static char16_t  c2 = u'\U00064321';     /* { dg-error "character not 
encodable in a single code unit" } */
 
 const static char16_t  c3 = 'a';
 const static char16_t  c4 = U'a';
@@ -14,5 +14,6 @@ const static char16_t c6 = U'\U00064321'
 const static char16_t  c7 = L'a';
 const static char16_t  c8 = L'\u2029';
 const static char16_t  c9 = L'\U00064321';     /* { dg-warning "conversion 
from .wchar_t. to .char16_t. changes value from .410401. to .17185." "" { 
target { 4byte_wchar_t } } } */
-                                               /* { dg-warning "constant too 
long" "" { target { ! 4byte_wchar_t } } .-1 } */
+                                               /* { dg-warning "character not 
encodable in a single code unit" "" { target { { ! 4byte_wchar_t } && 
c++20_down } } .-1 } */
+                                               /* { dg-error "character not 
encodable in a single code unit" "" { target { { ! 4byte_wchar_t } && c++23 } } 
.-2 } */
 int main () {}
--- gcc/testsuite/g++.dg/ext/utf32-4.C.jj       2020-01-14 20:02:46.841608965 
+0100
+++ gcc/testsuite/g++.dg/ext/utf32-4.C  2023-11-03 16:59:41.155924498 +0100
@@ -3,15 +3,16 @@
 /* { dg-do compile { target c++11 } } */
 
 const static char32_t  c0 = U'';               /* { dg-error "empty character" 
} */
-const static char32_t  c1 = U'ab';             /* { dg-error "constant too 
long" } */
+const static char32_t  c1 = U'ab';             /* { dg-error "multi-character 
literal cannot have an encoding prefix" } */
 const static char32_t  c2 = U'\U00064321';
 
 const static char32_t  c3 = 'a';
 const static char32_t  c4 = u'a';
 const static char32_t  c5 = u'\u2029';
-const static char32_t  c6 = u'\U00064321';     /* { dg-error "constant too 
long" } */
+const static char32_t  c6 = u'\U00064321';     /* { dg-error "character not 
encodable in a single code unit" } */
 const static char32_t  c7 = L'a';
 const static char32_t  c8 = L'\u2029';
-const static char32_t  c9 = L'\U00064321';     /* { dg-warning "constant too 
long" "" { target { ! 4byte_wchar_t } } } */  
+const static char32_t  c9 = L'\U00064321';     /* { dg-warning "character not 
encodable in a single code unit" "" { target { { ! 4byte_wchar_t } && 
c++20_down } } } */
+                                               /* { dg-error "character not 
encodable in a single code unit" "" { target { { ! 4byte_wchar_t } && c++23 } } 
.-1 } */
 
 int main () {}


        Jakub

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