printf: with \U, support all valid unicode points

Previously this was restricted to the C99 universal character subset,
which restricted most values <= 0x9F, as that simplifies the C lexer.
However printf(1) doesn't need this restriction.
Note also the bash builtin printf already supports all values <= 0x9F.

* src/printf.c (main): Relax the restriction on points <= 0x9F.
* doc/coreutils.texi (printf invocation): Adjust description.
* tests/misc/printf-cov.pl: Adjust accordingly.  Add new cases.
* NEWS: Mention the change in behavior.
Reported at https://bugs.debian.org/1022857

NEWS

@@ -41,6 +41,10 @@ GNU coreutils NEWS                                    -*- outline -*-
   reverting to the behavior in coreutils-9.0 and earlier.
   This behavior is now documented.
 
+  printf unicode \uNNNN, \UNNNNNNNN syntax, now supports all valid
+  unicode code points.  Previously is was restricted to the C
+  universal character subset, which restricted most points <= 0x9F.
+
   runcon now exits with status 125 for internal errors.  Previously upon
   internal errors it would exit with status 1, which was less distinguishable
   from errors from the invoked command.

doc/coreutils.texi

@@ -13209,16 +13209,16 @@ For example, @samp{printf '\400'} is equivalent to @samp{printf '\0'}.
 @cindex Unicode
 @cindex ISO/IEC 10646
 @vindex LC_CTYPE
-@command{printf} interprets two character syntaxes introduced in
-ISO C 99:
-@samp{\u} for 16-bit Unicode (ISO/IEC 10646)
-characters, specified as
+@command{printf} interprets two syntaxes for specifying Unicode
+(ISO/IEC 10646) characters.
+@samp{\u} for 16-bit Unicode characters, specified as
 four hexadecimal digits @var{hhhh}, and @samp{\U} for 32-bit Unicode
 characters, specified as eight hexadecimal digits @var{hhhhhhhh}.
 @command{printf} outputs the Unicode characters
-according to the @env{LC_CTYPE} locale.  Unicode characters in the ranges
-U+0000@dots{}U+009F, U+D800@dots{}U+DFFF cannot be specified by this syntax,
-except for U+0024 ($), U+0040 (@@), and U+0060 (@`).
+according to the @env{LC_CTYPE} locale.  Unicode characters in the range
+U+D800@dots{}U+DFFF cannot be specified by this syntax.
+This syntax fully supports the universal character subset
+introduced in ISO C 99.
 
 The processing of @samp{\u} and @samp{\U} requires a full-featured
 @code{iconv} facility.  It is activated on systems with glibc 2.2 (or newer),

src/printf.c

@@ -298,14 +298,9 @@ print_esc (char const *escstart, bool octal_0)
           uni_value = uni_value * 16 + hextobin (*p);
         }
 
-      /* A universal character name shall not specify a character short
-         identifier in the range 00000000 through 00000020, 0000007F through
-         0000009F, or 0000D800 through 0000DFFF inclusive. A universal
-         character name shall not designate a character in the required
-         character set.  */
-      if ((uni_value <= 0x9f
-           && uni_value != 0x24 && uni_value != 0x40 && uni_value != 0x60)
-          || (uni_value >= 0xd800 && uni_value <= 0xdfff))
+      /* Error for invalid code points 0000D800 through 0000DFFF inclusive.
+         Note print_unicode_char() would print the literal \u.. in this case. */
+      if (uni_value >= 0xd800 && uni_value <= 0xdfff)
         die (EXIT_FAILURE, 0, _("invalid universal character name \\%c%0*x"),
              esc_char, (esc_char == 'u' ? 4 : 8), uni_value);
 

tests/misc/printf-cov.pl

@@ -66,9 +66,14 @@ my @Tests =
   ['esc', q('\xaa\0377'),  {OUT=>"\xaa\0377"}],
   ['esc-bad-hex', q('\x'), {EXIT=>1},
     {ERR=>"$prog: missing hexadecimal number in escape\n"}],
-  # ['u4', q('\u09ac'), {OUT=>"\xe0a6ac"}],
-  ['u-invalid', q('\u0000'), {EXIT=>1},
-    {ERR=>"$prog: invalid universal character name \\u0000\n"}],
+  ['u-bad-hex', q('\u00'), {EXIT=>1},
+    {ERR=>"$prog: missing hexadecimal number in escape\n"}],
+  ['U-bad-hex', q('\U0000'), {EXIT=>1},
+    {ERR=>"$prog: missing hexadecimal number in escape\n"}],
+  ['u4', q('\u0030'), {OUT=>"0"}],
+  ['U8', q('\U00000030'), {OUT=>"0"}],
+  ['u-invalid', q('\ud800'), {EXIT=>1},
+    {ERR=>"$prog: invalid universal character name \\ud800\n"}],
   ['u-missing', q('\u'), {EXIT=>1},
     {ERR=>"$prog: missing hexadecimal number in escape\n"}],
   ['d-invalid', '%d no-num', {OUT=>'0'}, {EXIT=>1},