[v7] POSIX locale covers every byte [BZ# 29511]

Message ID 20221109161415.eyqgyrp2jlwzfdmb@tarta.nabijaczleweli.xyz
State Under Review
Delegated to: Florian Weimer
Headers
Series [v7] POSIX locale covers every byte [BZ# 29511] |

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Commit Message

наб Nov. 9, 2022, 4:14 p.m. UTC
  Hi!

On Wed, Nov 09, 2022 at 03:20:26PM +0100, Florian Weimer wrote:
> * наб:
> > This is a logistically trivial patch,
> > largely duplicating the extant ASCII code with the error path changed
> I wouldn't say it's trivial in the commit message. 8-)
Trimmed to ~second line

> > There are two user-facing changes:
> >   * nl_langinfo(CODESET) is "POSIX" instead of "ANSI_X3.4-1968"
> >   * mbrtowc() and friends return b if b <= 0x7F else <UDF00>+b
> >
> > Since Issue 7 TC 2/Issue 8, the C/POSIX locale, effectively,
> >   (a) is 1-byte, stateless, and contains 256 characters
> >   (b) they collate in byte order
> >   (c) the first 128 characters are equivalent to ASCII (like previous)
> > cf. https://www.austingroupbugs.net/view.php?id=663 for a summary of
> > changes to the standard;
> > in short, this means that mbrtowc() must never fail and must return
> >   b if b <= 0x7F else ab+c for all bytes b
> >   where c is some constant >=0x80
> >     and a is a positive integer constant
> >
> > By strategically picking c=<UDF00> we land at the tail-end of the
> > Unicode Low Surrogate Area at DC00-DFFF, described as
> >   > Isolated surrogate code points have no interpretation;
> >   > consequently, no character code charts or names lists
> >   > are provided for this range.
> > and match musl
> 
> Sadly this doesn't match Python and PEP 540:
> 
> >>> b'\x80'.decode('UTF-8', errors='surrogateescape')
> '\udc80'
> 
> I believe the implementation translates this to 0xDF80 instead.
Yes.

> Not sure what is more important here, musl compatibility or Python
> compatibility.  Cc:ing Victor in case he as comments.  I should probably
> ask on the musl list as well as how this divergence came to pass.
I went for musl because (a) it's a libc not some random programming
language, (b) putting the end of our domain at the end of the
surrogates is more aesthetically and ideologically pleasing, and (c)
there's marginal value of having both musl and glibc produce the same
characters if you like save them as integers for some reason.
But the choice of any range therein is pretty much editorial, I think.

> This change definitely needs a NEWS entry.
Something like this?
  Deprecated and removed features, and other changes affecting compatibility:
  * The default/"POSIX"/"C" locale's character set is now "POSIX",
    instead of "ANSI_X3.4-1968"  this is a new fully-reversible
    8-bit transparent encoding for compatibility with Issue 7 TC 2,
    identity-mapping bytes in the ASCII [0, 0x7F] range,
    and mapping [0x80, 0xFF] bytes to [<U+DF80>, <U+DFFF>].

> > diff --git a/iconv/gconv_int.h b/iconv/gconv_int.h
> > index 1c6745043e..45ab1edfad 100644
> > --- a/iconv/gconv_int.h
> > +++ b/iconv/gconv_int.h
> > @@ -299,6 +301,11 @@ __BUILTIN_TRANSFORM (__gconv_transform_utf16_internal);
> >     only ASCII characters.  */
> >  extern wint_t __gconv_btwoc_ascii (struct __gconv_step *step, unsigned char c);
> >  
> > +/* Specialized conversion function for a single byte to INTERNAL,
> > +   identity-mapping bytes [0, 0x7F], and moving [0x80, 0xFF] into the end
> > +   of the Low Surrogate Area at [U+DF80, U+DFFF].  */
> > +extern wint_t __gconv_btwoc_posix (struct __gconv_step *step, unsigned char c);
> > +
> >  #endif
> 
> Missing attribute_hidden.  Yes, it's also missing from
> __gconv_btwoc_ascii.  The linker probably papers over it.
Added.

> > diff --git a/iconv/gconv_posix.c b/iconv/gconv_posix.c
> > new file mode 100644
> > index 0000000000..dcb13fbb43
> > --- /dev/null
> > +++ b/iconv/gconv_posix.c
> > @@ -0,0 +1,96 @@
> > +/* Simple transformations functions.
> 
> I think this line should say something about surrogate-escape encoding
> for the POSIX locale.
I completely missed that this line isn't part of the licence. Used
> "POSIX" locale transformation functions.
as the shorthand, this is expounded in the comment for __g_b_p() below.

> > +    else								      \
> > +      {									      \
> > +	if (__glibc_unlikely (val > 0x7f))				      \
> > +	  val -= 0xdf00;						      \
> > +	*outptr++ = val;						      \
> > +	inptr += sizeof (uint32_t);					      \
> > +      }									      \
> > +  }
> 
> I suggest to drop the last __glibc_unlikely here because it's
> input-dependent.
Applied.

> > diff --git a/locale/tst-C-locale.c b/locale/tst-C-locale.c
> > index 6bd0367069..f30396ae12 100644
> > --- a/locale/tst-C-locale.c
> > +++ b/locale/tst-C-locale.c
> > @@ -229,6 +229,75 @@ run_test (const char *locname)
> >    STRTEST (YESSTR, "");
> >    STRTEST (NOSTR, "");
> >  
> > +#define CONVTEST(b, v) \
> > +  {									      \
> > +    unsigned char bs[] = {b, 0};					      \
> > +    mbstate_t ctx = {};							      \
> > +    wchar_t wc = -1;							      \
> > +    size_t sz = mbrtowc(&wc, (char *) bs, 1, &ctx);			      \
> 
> Missing space before '(' (also in other cases below).
> 
> Not sure if the macros are needed, maybe write one loop for each
> direction with a condition in it?
Fixed, unrolled.

> > diff --git a/stdio-common/tst-printf-bz25691.c b/stdio-common/tst-printf-bz25691.c
> > index 44844e71c3..e66242b58f 100644
> > --- a/stdio-common/tst-printf-bz25691.c
> > +++ b/stdio-common/tst-printf-bz25691.c
> > @@ -30,6 +30,8 @@
> >  static int
> >  do_test (void)
> >  {
> > +  setlocale(LC_CTYPE, "C.UTF-8");
> > +
> >    mtrace ();
> >  
> >    /* For 's' conversion specifier with 'l' modifier the array must be
> 
> What's the rationale for this change?  If it is really required, you
> must also update stdio-common/Makefile with a new dependency on
> $(gen-locales).
The test depends on the locale having a hole at 0xFF, cf. ll. 93-100:
    /* Same test, but with an invalid multibyte sequence.  */
    mbs[mbssize - 2] = 0xff;

    ret = swprintf (result, resultsize, L"%.65537s", mbs);
    TEST_COMPARE (ret, -1);

    ret = swprintf (result, resultsize, L"%1$.65537s", mbs);
    TEST_COMPARE (ret, -1);
And this is the simplest way to ensure that, I think.

Dependency added.

> Thanks,
> Florian
Best,
наб

Scissor-patch follows.
-- >8 --
This largely duplicates the ASCII code with the error path changed

There are two user-facing changes:
  * nl_langinfo(CODESET) is "POSIX" instead of "ANSI_X3.4-1968"
  * mbrtowc() and friends return b if b <= 0x7F else <UDF00>+b

Since Issue 7 TC 2/Issue 8, the C/POSIX locale, effectively,
  (a) is 1-byte, stateless, and contains 256 characters
  (b) they collate in byte order
  (c) the first 128 characters are equivalent to ASCII (like previous)
cf. https://www.austingroupbugs.net/view.php?id=663 for a summary of
changes to the standard;
in short, this means that mbrtowc() must never fail and must return
  b if b <= 0x7F else ab+c for all bytes b
  where c is some constant >=0x80
    and a is a positive integer constant

By strategically picking c=<UDF00> we land at the tail-end of the
Unicode Low Surrogate Area at DC00-DFFF, described as
  > Isolated surrogate code points have no interpretation;
  > consequently, no character code charts or names lists
  > are provided for this range.
and match musl

Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
---
 iconv/Makefile                    |   2 +-
 iconv/gconv_builtin.h             |   8 ++
 iconv/gconv_int.h                 |   8 ++
 iconv/gconv_posix.c               |  96 ++++++++++++++++++++
 iconv/tst-iconv_prog.sh           |  43 +++++++++
 iconvdata/tst-tables.sh           |   1 +
 inet/tst-idna_name_classify.c     |   6 +-
 locale/tst-C-locale.c             |  44 +++++++++
 localedata/charmaps/POSIX         | 136 ++++++++++++++++++++++++++++
 localedata/locales/POSIX          | 143 +++++++++++++++++++++++++++++-
 stdio-common/Makefile             |   1 +
 stdio-common/tst-printf-bz25691.c |   2 +
 wcsmbs/wcsmbsload.c               |  14 +--
 13 files changed, 493 insertions(+), 11 deletions(-)
 create mode 100644 iconv/gconv_posix.c
 create mode 100644 localedata/charmaps/POSIX
  

Comments

Florian Weimer Nov. 10, 2022, 9:52 a.m. UTC | #1
* наб:

>> Not sure what is more important here, musl compatibility or Python
>> compatibility.  Cc:ing Victor in case he as comments.  I should probably
>> ask on the musl list as well as how this divergence came to pass.

> I went for musl because (a) it's a libc not some random programming
> language, (b) putting the end of our domain at the end of the
> surrogates is more aesthetically and ideologically pleasing, and (c)
> there's marginal value of having both musl and glibc produce the same
> characters if you like save them as integers for some reason.
> But the choice of any range therein is pretty much editorial, I think.

Let's wait and see what the musl folks say.

>> This change definitely needs a NEWS entry.
> Something like this?
>   Deprecated and removed features, and other changes affecting compatibility:
>   * The default/"POSIX"/"C" locale's character set is now "POSIX",
>     instead of "ANSI_X3.4-1968"  this is a new fully-reversible
>     8-bit transparent encoding for compatibility with Issue 7 TC 2,

“POSIX Issue 7 TC 2”

>     identity-mapping bytes in the ASCII [0, 0x7F] range,
>     and mapping [0x80, 0xFF] bytes to [<U+DF80>, <U+DFFF>].

It should go into the major new features section, I think.

I would also say that POSIX no longer allows using UTF-8 for the C/POSIX
locale because the obvious question will be “why this custom encoding
and not UTF-8?”.  This new POSIX requirement is still a major
disappointment to me.

No need to repost for now.

>> > diff --git a/stdio-common/tst-printf-bz25691.c b/stdio-common/tst-printf-bz25691.c
>> > index 44844e71c3..e66242b58f 100644
>> > --- a/stdio-common/tst-printf-bz25691.c
>> > +++ b/stdio-common/tst-printf-bz25691.c
>> > @@ -30,6 +30,8 @@
>> >  static int
>> >  do_test (void)
>> >  {
>> > +  setlocale(LC_CTYPE, "C.UTF-8");
>> > +
>> >    mtrace ();
>> >  
>> >    /* For 's' conversion specifier with 'l' modifier the array must be
>> 
>> What's the rationale for this change?  If it is really required, you
>> must also update stdio-common/Makefile with a new dependency on
>> $(gen-locales).
> The test depends on the locale having a hole at 0xFF, cf. ll. 93-100:
>     /* Same test, but with an invalid multibyte sequence.  */
>     mbs[mbssize - 2] = 0xff;
>
>     ret = swprintf (result, resultsize, L"%.65537s", mbs);
>     TEST_COMPARE (ret, -1);
>
>     ret = swprintf (result, resultsize, L"%1$.65537s", mbs);
>     TEST_COMPARE (ret, -1);
> And this is the simplest way to ensure that, I think.
>
> Dependency added.

Right, makes sense.

Thanks,
Florian
  

Patch

diff --git a/iconv/Makefile b/iconv/Makefile
index a0d90cfeac..6e926f53e3 100644
--- a/iconv/Makefile
+++ b/iconv/Makefile
@@ -25,7 +25,7 @@  include ../Makeconfig
 headers		= iconv.h gconv.h
 routines	= iconv_open iconv iconv_close \
 		  gconv_open gconv gconv_close gconv_db gconv_conf \
-		  gconv_builtin gconv_simple gconv_trans gconv_cache
+		  gconv_builtin gconv_simple gconv_posix gconv_trans gconv_cache
 routines	+= gconv_dl gconv_charset
 
 vpath %.c ../locale/programs ../intl
diff --git a/iconv/gconv_builtin.h b/iconv/gconv_builtin.h
index 68c2369b1f..cd1805b3ce 100644
--- a/iconv/gconv_builtin.h
+++ b/iconv/gconv_builtin.h
@@ -89,6 +89,14 @@  BUILTIN_TRANSFORMATION ("INTERNAL", "ANSI_X3.4-1968//", 1, "=INTERNAL->ascii",
 			__gconv_transform_internal_ascii, NULL, 4, 4, 1, 1)
 
 
+BUILTIN_TRANSFORMATION ("POSIX//", "INTERNAL", 1, "=posix->INTERNAL",
+			__gconv_transform_posix_internal, __gconv_btwoc_posix,
+			1, 1, 4, 4)
+
+BUILTIN_TRANSFORMATION ("INTERNAL", "POSIX//", 1, "=INTERNAL->posix",
+			__gconv_transform_internal_posix, NULL, 4, 4, 1, 1)
+
+
 #if BYTE_ORDER == BIG_ENDIAN
 BUILTIN_ALIAS ("UNICODEBIG//", "ISO-10646/UCS2/")
 BUILTIN_ALIAS ("UCS-2BE//", "ISO-10646/UCS2/")
diff --git a/iconv/gconv_int.h b/iconv/gconv_int.h
index 1c6745043e..2f21a7389d 100644
--- a/iconv/gconv_int.h
+++ b/iconv/gconv_int.h
@@ -281,6 +281,8 @@  extern int __gconv_compare_alias (const char *name1, const char *name2)
 
 __BUILTIN_TRANSFORM (__gconv_transform_ascii_internal);
 __BUILTIN_TRANSFORM (__gconv_transform_internal_ascii);
+__BUILTIN_TRANSFORM (__gconv_transform_posix_internal);
+__BUILTIN_TRANSFORM (__gconv_transform_internal_posix);
 __BUILTIN_TRANSFORM (__gconv_transform_utf8_internal);
 __BUILTIN_TRANSFORM (__gconv_transform_internal_utf8);
 __BUILTIN_TRANSFORM (__gconv_transform_ucs2_internal);
@@ -299,6 +301,12 @@  __BUILTIN_TRANSFORM (__gconv_transform_utf16_internal);
    only ASCII characters.  */
 extern wint_t __gconv_btwoc_ascii (struct __gconv_step *step, unsigned char c);
 
+/* Specialized conversion function for a single byte to INTERNAL,
+   identity-mapping bytes [0, 0x7F], and moving [0x80, 0xFF] into the end
+   of the Low Surrogate Area at [U+DF80, U+DFFF].  */
+extern wint_t __gconv_btwoc_posix (struct __gconv_step *step, unsigned char c)
+     attribute_hidden;
+
 #endif
 
 __END_DECLS
diff --git a/iconv/gconv_posix.c b/iconv/gconv_posix.c
new file mode 100644
index 0000000000..412d910109
--- /dev/null
+++ b/iconv/gconv_posix.c
@@ -0,0 +1,96 @@ 
+/* "POSIX" locale transformation functions.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+
+#include <gconv_int.h>
+
+
+/* Specialized conversion function for a single byte to INTERNAL,
+   identity-mapping bytes [0, 0x7F], and moving [0x80, 0xFF] into the end
+   of the Low Surrogate Area at [U+DF80, U+DFFF].  */
+wint_t
+__gconv_btwoc_posix (struct __gconv_step *step, unsigned char c)
+{
+  if (c < 0x80)
+    return c;
+  else
+    return 0xdf00 + c;
+}
+
+
+/* Convert from {[0, 0x7F] => ISO 646-IRV; [0x80, 0xFF] => [U+DF80, U+DFFF]}
+   to the internal (UCS4-like) format.  */
+#define DEFINE_INIT		0
+#define DEFINE_FINI		0
+#define MIN_NEEDED_FROM		1
+#define MIN_NEEDED_TO		4
+#define FROM_DIRECTION		1
+#define FROM_LOOP		posix_internal_loop
+#define TO_LOOP			posix_internal_loop /* This is not used.  */
+#define FUNCTION_NAME		__gconv_transform_posix_internal
+#define ONE_DIRECTION		1
+
+#define MIN_NEEDED_INPUT	MIN_NEEDED_FROM
+#define MIN_NEEDED_OUTPUT	MIN_NEEDED_TO
+#define LOOPFCT			FROM_LOOP
+#define BODY \
+  {									      \
+    if (__glibc_unlikely (*inptr > '\x7f'))				      \
+      *((uint32_t *) outptr) = 0xdf00 + *inptr++;			      \
+    else								      \
+      *((uint32_t *) outptr) = *inptr++;				      \
+    outptr += sizeof (uint32_t);					      \
+  }
+#include <iconv/loop.c>
+#include <iconv/skeleton.c>
+
+
+/* Convert from the internal (UCS4-like) format to
+   {ISO 646-IRV => [0, 0x7F]; [U+DF80, U+DFFF] => [0x80, 0xFF]}.  */
+#define DEFINE_INIT		0
+#define DEFINE_FINI		0
+#define MIN_NEEDED_FROM		4
+#define MIN_NEEDED_TO		1
+#define FROM_DIRECTION		1
+#define FROM_LOOP		internal_posix_loop
+#define TO_LOOP			internal_posix_loop /* This is not used.  */
+#define FUNCTION_NAME		__gconv_transform_internal_posix
+#define ONE_DIRECTION		1
+
+#define MIN_NEEDED_INPUT	MIN_NEEDED_FROM
+#define MIN_NEEDED_OUTPUT	MIN_NEEDED_TO
+#define LOOPFCT			FROM_LOOP
+#define BODY \
+  {									      \
+    uint32_t val = *((const uint32_t *) inptr);				      \
+    if (__glibc_unlikely ((val > 0x7f && val < 0xdf80) || val > 0xdfff))      \
+      {									      \
+	UNICODE_TAG_HANDLER (val, 4);					      \
+	STANDARD_TO_LOOP_ERR_HANDLER (4);				      \
+      }									      \
+    else								      \
+      {									      \
+	if (val > 0x7f)							      \
+	  val -= 0xdf00;						      \
+	*outptr++ = val;						      \
+	inptr += sizeof (uint32_t);					      \
+      }									      \
+  }
+#define LOOP_NEED_FLAGS
+#include <iconv/loop.c>
+#include <iconv/skeleton.c>
diff --git a/iconv/tst-iconv_prog.sh b/iconv/tst-iconv_prog.sh
index b3d8bf5110..a24d8d2207 100644
--- a/iconv/tst-iconv_prog.sh
+++ b/iconv/tst-iconv_prog.sh
@@ -285,3 +285,46 @@  for errorcommand in "${errorarray[@]}"; do
   execute_test
   check_errtest_result
 done
+
+allbytes ()
+{
+  for (( i = 0; i <= 255; i++ )); do
+    printf '\'"$(printf "%o" "$i")"
+  done
+}
+
+allucs4be ()
+{
+  for (( i = 0; i <= 127; i++ )); do
+    printf '\0\0\0\'"$(printf "%o" "$i")"
+  done
+  for (( i = 128; i <= 255; i++ )); do
+    printf '\0\0\xdf\'"$(printf "%o" "$i")"
+  done
+}
+
+check_posix_result ()
+{
+  if [ $? -eq 0 ]; then
+    result=PASS
+  else
+    result=FAIL
+  fi
+
+  echo "$result: from \"$1\", to: \"$2\""
+
+  if [ "$result" != "PASS" ]; then
+    exit 1
+  fi
+}
+
+check_posix_encoding ()
+{
+  eval PROG=\"$ICONV\"
+  allbytes  | $PROG -f POSIX -t UCS-4BE | cmp -s - <(allucs4be)
+  check_posix_result POSIX UCS-4BE
+  allucs4be | $PROG -f UCS-4BE -t POSIX | cmp -s - <(allbytes)
+  check_posix_result UCS-4BE POSIX
+}
+
+check_posix_encoding
diff --git a/iconvdata/tst-tables.sh b/iconvdata/tst-tables.sh
index 4207b44175..33a02158ac 100755
--- a/iconvdata/tst-tables.sh
+++ b/iconvdata/tst-tables.sh
@@ -31,6 +31,7 @@  cat <<EOF |
   # Keep this list in the same order as gconv-modules.
   #
   # charset name    table name          comment
+  POSIX
   ASCII             ANSI_X3.4-1968
   ISO646-GB         BS_4730
   ISO646-CA         CSA_Z243.4-1985-1
diff --git a/inet/tst-idna_name_classify.c b/inet/tst-idna_name_classify.c
index bfd34eee31..b379481844 100644
--- a/inet/tst-idna_name_classify.c
+++ b/inet/tst-idna_name_classify.c
@@ -37,11 +37,11 @@  do_test (void)
   puts ("info: C locale tests");
   locale_insensitive_tests ();
   TEST_COMPARE (__idna_name_classify ("abc\200def"),
-                idna_name_encoding_error);
+                idna_name_nonascii);
   TEST_COMPARE (__idna_name_classify ("abc\200\\def"),
-                idna_name_encoding_error);
+                idna_name_nonascii_backslash);
   TEST_COMPARE (__idna_name_classify ("abc\377def"),
-                idna_name_encoding_error);
+                idna_name_nonascii);
 
   puts ("info: en_US.ISO-8859-1 locale tests");
   if (setlocale (LC_CTYPE, "en_US.ISO-8859-1") == 0)
diff --git a/locale/tst-C-locale.c b/locale/tst-C-locale.c
index 6bd0367069..0f03d69003 100644
--- a/locale/tst-C-locale.c
+++ b/locale/tst-C-locale.c
@@ -20,6 +20,7 @@ 
 #include <langinfo.h>
 #include <limits.h>
 #include <locale.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 #include <wchar.h>
@@ -229,6 +230,49 @@  run_test (const char *locname)
   STRTEST (YESSTR, "");
   STRTEST (NOSTR, "");
 
+  for(int i = 0; i <= 0xff; ++i)
+    {
+      unsigned char bs[] = {i, 0};
+      mbstate_t ctx = {};
+      wchar_t wc = -1, exp = i <= 0x7f ? i : (0xdf00 + i);
+      size_t sz = mbrtowc(&wc, (char *) bs, 1, &ctx);
+      if (sz != !!i)
+	{
+	  printf ("mbrtowc(%02hhx) width in locale %s wrong "
+		  "(is %zd, should be %d)\n", *bs, locname, sz, !!i);
+	  result = 1;
+	}
+      if (wc != exp)
+	{
+	  printf ("mbrtowc(%02hhx) value in locale %s wrong "
+		  "(is %x, should be %x)\n", *bs, locname, wc, exp);
+	  result = 1;
+	}
+    }
+
+  for (int i = 0; i <= 0xffff; ++i)
+    {
+      bool expok = (i <= 0x7f) || (i >= 0xdf80 && i <= 0xdfff);
+      size_t expsz = expok ? 1 : (size_t) -1;
+      unsigned char expob = expok ? (i & 0xff) : (unsigned char) -1;
+
+      unsigned char ob = -1;
+      mbstate_t ctx = {};
+      size_t sz = wcrtomb ((char *) &ob, i, &ctx);
+      if (sz != expsz)
+	{
+	  printf ("wcrtomb(%x) width in locale %s wrong "
+		  "(is %zd, should be %zd)\n", i, locname, sz, expsz);
+	  result = 1;
+	}
+      if (ob != expob)
+	{
+	  printf ("wcrtomb(%x) value in locale %s wrong "
+		  "(is %hhx, should be %hhx)\n", i, locname, ob, expob);
+	  result = 1;
+	}
+    }
+
   /* Test the new locale mechanisms.  */
   loc = newlocale (LC_ALL_MASK, locname, NULL);
   if (loc == NULL)
diff --git a/localedata/charmaps/POSIX b/localedata/charmaps/POSIX
new file mode 100644
index 0000000000..c44007ff49
--- /dev/null
+++ b/localedata/charmaps/POSIX
@@ -0,0 +1,136 @@ 
+<code_set_name> POSIX
+<comment_char> %
+<escape_char> /
+% source: cf. localedata/locales/POSIX, LC_COLLATE
+
+CHARMAP
+<U0000>     /x00         NULL (NUL)
+<U0001>     /x01         START OF HEADING (SOH)
+<U0002>     /x02         START OF TEXT (STX)
+<U0003>     /x03         END OF TEXT (ETX)
+<U0004>     /x04         END OF TRANSMISSION (EOT)
+<U0005>     /x05         ENQUIRY (ENQ)
+<U0006>     /x06         ACKNOWLEDGE (ACK)
+<U0007>     /x07         BELL (BEL)
+<U0008>     /x08         BACKSPACE (BS)
+<U0009>     /x09         CHARACTER TABULATION (HT)
+<U000A>     /x0a         LINE FEED (LF)
+<U000B>     /x0b         LINE TABULATION (VT)
+<U000C>     /x0c         FORM FEED (FF)
+<U000D>     /x0d         CARRIAGE RETURN (CR)
+<U000E>     /x0e         SHIFT OUT (SO)
+<U000F>     /x0f         SHIFT IN (SI)
+<U0010>     /x10         DATALINK ESCAPE (DLE)
+<U0011>     /x11         DEVICE CONTROL ONE (DC1)
+<U0012>     /x12         DEVICE CONTROL TWO (DC2)
+<U0013>     /x13         DEVICE CONTROL THREE (DC3)
+<U0014>     /x14         DEVICE CONTROL FOUR (DC4)
+<U0015>     /x15         NEGATIVE ACKNOWLEDGE (NAK)
+<U0016>     /x16         SYNCHRONOUS IDLE (SYN)
+<U0017>     /x17         END OF TRANSMISSION BLOCK (ETB)
+<U0018>     /x18         CANCEL (CAN)
+<U0019>     /x19         END OF MEDIUM (EM)
+<U001A>     /x1a         SUBSTITUTE (SUB)
+<U001B>     /x1b         ESCAPE (ESC)
+<U001C>     /x1c         FILE SEPARATOR (IS4)
+<U001D>     /x1d         GROUP SEPARATOR (IS3)
+<U001E>     /x1e         RECORD SEPARATOR (IS2)
+<U001F>     /x1f         UNIT SEPARATOR (IS1)
+<U0020>     /x20         SPACE
+<U0021>     /x21         EXCLAMATION MARK
+<U0022>     /x22         QUOTATION MARK
+<U0023>     /x23         NUMBER SIGN
+<U0024>     /x24         DOLLAR SIGN
+<U0025>     /x25         PERCENT SIGN
+<U0026>     /x26         AMPERSAND
+<U0027>     /x27         APOSTROPHE
+<U0028>     /x28         LEFT PARENTHESIS
+<U0029>     /x29         RIGHT PARENTHESIS
+<U002A>     /x2a         ASTERISK
+<U002B>     /x2b         PLUS SIGN
+<U002C>     /x2c         COMMA
+<U002D>     /x2d         HYPHEN-MINUS
+<U002E>     /x2e         FULL STOP
+<U002F>     /x2f         SOLIDUS
+<U0030>     /x30         DIGIT ZERO
+<U0031>     /x31         DIGIT ONE
+<U0032>     /x32         DIGIT TWO
+<U0033>     /x33         DIGIT THREE
+<U0034>     /x34         DIGIT FOUR
+<U0035>     /x35         DIGIT FIVE
+<U0036>     /x36         DIGIT SIX
+<U0037>     /x37         DIGIT SEVEN
+<U0038>     /x38         DIGIT EIGHT
+<U0039>     /x39         DIGIT NINE
+<U003A>     /x3a         COLON
+<U003B>     /x3b         SEMICOLON
+<U003C>     /x3c         LESS-THAN SIGN
+<U003D>     /x3d         EQUALS SIGN
+<U003E>     /x3e         GREATER-THAN SIGN
+<U003F>     /x3f         QUESTION MARK
+<U0040>     /x40         COMMERCIAL AT
+<U0041>     /x41         LATIN CAPITAL LETTER A
+<U0042>     /x42         LATIN CAPITAL LETTER B
+<U0043>     /x43         LATIN CAPITAL LETTER C
+<U0044>     /x44         LATIN CAPITAL LETTER D
+<U0045>     /x45         LATIN CAPITAL LETTER E
+<U0046>     /x46         LATIN CAPITAL LETTER F
+<U0047>     /x47         LATIN CAPITAL LETTER G
+<U0048>     /x48         LATIN CAPITAL LETTER H
+<U0049>     /x49         LATIN CAPITAL LETTER I
+<U004A>     /x4a         LATIN CAPITAL LETTER J
+<U004B>     /x4b         LATIN CAPITAL LETTER K
+<U004C>     /x4c         LATIN CAPITAL LETTER L
+<U004D>     /x4d         LATIN CAPITAL LETTER M
+<U004E>     /x4e         LATIN CAPITAL LETTER N
+<U004F>     /x4f         LATIN CAPITAL LETTER O
+<U0050>     /x50         LATIN CAPITAL LETTER P
+<U0051>     /x51         LATIN CAPITAL LETTER Q
+<U0052>     /x52         LATIN CAPITAL LETTER R
+<U0053>     /x53         LATIN CAPITAL LETTER S
+<U0054>     /x54         LATIN CAPITAL LETTER T
+<U0055>     /x55         LATIN CAPITAL LETTER U
+<U0056>     /x56         LATIN CAPITAL LETTER V
+<U0057>     /x57         LATIN CAPITAL LETTER W
+<U0058>     /x58         LATIN CAPITAL LETTER X
+<U0059>     /x59         LATIN CAPITAL LETTER Y
+<U005A>     /x5a         LATIN CAPITAL LETTER Z
+<U005B>     /x5b         LEFT SQUARE BRACKET
+<U005C>     /x5c         REVERSE SOLIDUS
+<U005D>     /x5d         RIGHT SQUARE BRACKET
+<U005E>     /x5e         CIRCUMFLEX ACCENT
+<U005F>     /x5f         LOW LINE
+<U0060>     /x60         GRAVE ACCENT
+<U0061>     /x61         LATIN SMALL LETTER A
+<U0062>     /x62         LATIN SMALL LETTER B
+<U0063>     /x63         LATIN SMALL LETTER C
+<U0064>     /x64         LATIN SMALL LETTER D
+<U0065>     /x65         LATIN SMALL LETTER E
+<U0066>     /x66         LATIN SMALL LETTER F
+<U0067>     /x67         LATIN SMALL LETTER G
+<U0068>     /x68         LATIN SMALL LETTER H
+<U0069>     /x69         LATIN SMALL LETTER I
+<U006A>     /x6a         LATIN SMALL LETTER J
+<U006B>     /x6b         LATIN SMALL LETTER K
+<U006C>     /x6c         LATIN SMALL LETTER L
+<U006D>     /x6d         LATIN SMALL LETTER M
+<U006E>     /x6e         LATIN SMALL LETTER N
+<U006F>     /x6f         LATIN SMALL LETTER O
+<U0070>     /x70         LATIN SMALL LETTER P
+<U0071>     /x71         LATIN SMALL LETTER Q
+<U0072>     /x72         LATIN SMALL LETTER R
+<U0073>     /x73         LATIN SMALL LETTER S
+<U0074>     /x74         LATIN SMALL LETTER T
+<U0075>     /x75         LATIN SMALL LETTER U
+<U0076>     /x76         LATIN SMALL LETTER V
+<U0077>     /x77         LATIN SMALL LETTER W
+<U0078>     /x78         LATIN SMALL LETTER X
+<U0079>     /x79         LATIN SMALL LETTER Y
+<U007A>     /x7a         LATIN SMALL LETTER Z
+<U007B>     /x7b         LEFT CURLY BRACKET
+<U007C>     /x7c         VERTICAL LINE
+<U007D>     /x7d         RIGHT CURLY BRACKET
+<U007E>     /x7e         TILDE
+<U007F>     /x7f         DELETE (DEL)
+<UDF80>..<UDFFF> /x80
+END CHARMAP
diff --git a/localedata/locales/POSIX b/localedata/locales/POSIX
index 7ec7f1c577..fc34a6abc1 100644
--- a/localedata/locales/POSIX
+++ b/localedata/locales/POSIX
@@ -97,6 +97,20 @@  END LC_CTYPE
 LC_COLLATE
 % This is the POSIX Locale definition for the LC_COLLATE category.
 % The order is the same as in the ASCII code set.
+% Values above <DEL> (<U007F>) inserted in order, per Issue 7 TC2,
+% XBD, 7.3.2, LC_COLLATE Category in the POSIX Locale:
+% > All characters not explicitly listed here shall be inserted
+% > in the character collation order after the listed characters
+% > and shall be assigned unique primary weights. If the listed
+% > characters have ASCII encoding, the other characters shall
+% > be in ascending order according to their coded character set values
+% Since Issue 7 TC2 (XBD, 6.2 Character Encoding):
+% > The POSIX locale shall contain 256 single-byte characters [...]
+% (cf. bug 663, 674).
+% this is in contrast to previous issues, which limited the POSIX
+% locale to the Portable Character Set (7-bit ASCII).
+% We use the end of the Low Surrogate Area to contain these,
+% yielding [<UDF80>, <UDFFF>]
 order_start forward
 <U0000>
 <U0001>
@@ -226,7 +240,134 @@  order_start forward
 <U007D>
 <U007E>
 <U007F>
-UNDEFINED
+<UDF80>
+<UDF81>
+<UDF82>
+<UDF83>
+<UDF84>
+<UDF85>
+<UDF86>
+<UDF87>
+<UDF88>
+<UDF89>
+<UDF8A>
+<UDF8B>
+<UDF8C>
+<UDF8D>
+<UDF8E>
+<UDF8F>
+<UDF90>
+<UDF91>
+<UDF92>
+<UDF93>
+<UDF94>
+<UDF95>
+<UDF96>
+<UDF97>
+<UDF98>
+<UDF99>
+<UDF9A>
+<UDF9B>
+<UDF9C>
+<UDF9D>
+<UDF9E>
+<UDF9F>
+<UDFA0>
+<UDFA1>
+<UDFA2>
+<UDFA3>
+<UDFA4>
+<UDFA5>
+<UDFA6>
+<UDFA7>
+<UDFA8>
+<UDFA9>
+<UDFAA>
+<UDFAB>
+<UDFAC>
+<UDFAD>
+<UDFAE>
+<UDFAF>
+<UDFB0>
+<UDFB1>
+<UDFB2>
+<UDFB3>
+<UDFB4>
+<UDFB5>
+<UDFB6>
+<UDFB7>
+<UDFB8>
+<UDFB9>
+<UDFBA>
+<UDFBB>
+<UDFBC>
+<UDFBD>
+<UDFBE>
+<UDFBF>
+<UDFC0>
+<UDFC1>
+<UDFC2>
+<UDFC3>
+<UDFC4>
+<UDFC5>
+<UDFC6>
+<UDFC7>
+<UDFC8>
+<UDFC9>
+<UDFCA>
+<UDFCB>
+<UDFCC>
+<UDFCD>
+<UDFCE>
+<UDFCF>
+<UDFD0>
+<UDFD1>
+<UDFD2>
+<UDFD3>
+<UDFD4>
+<UDFD5>
+<UDFD6>
+<UDFD7>
+<UDFD8>
+<UDFD9>
+<UDFDA>
+<UDFDB>
+<UDFDC>
+<UDFDD>
+<UDFDE>
+<UDFDF>
+<UDFE0>
+<UDFE1>
+<UDFE2>
+<UDFE3>
+<UDFE4>
+<UDFE5>
+<UDFE6>
+<UDFE7>
+<UDFE8>
+<UDFE9>
+<UDFEA>
+<UDFEB>
+<UDFEC>
+<UDFED>
+<UDFEE>
+<UDFEF>
+<UDFF0>
+<UDFF1>
+<UDFF2>
+<UDFF3>
+<UDFF4>
+<UDFF5>
+<UDFF6>
+<UDFF7>
+<UDFF8>
+<UDFF9>
+<UDFFA>
+<UDFFB>
+<UDFFC>
+<UDFFD>
+<UDFFE>
+<UDFFF>
 order_end
 %
 END LC_COLLATE
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index 401dac69de..3cd6c3dc56 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -305,6 +305,7 @@  $(objpfx)scanf13.out: $(gen-locales)
 $(objpfx)test-vfprintf.out: $(gen-locales)
 $(objpfx)tst-grouping.out: $(gen-locales)
 $(objpfx)tst-grouping2.out: $(gen-locales)
+$(objpfx)tst-printf-bz25691-mem.out: $(gen-locales)
 $(objpfx)tst-sprintf.out: $(gen-locales)
 $(objpfx)tst-sscanf.out: $(gen-locales)
 $(objpfx)tst-swprintf.out: $(gen-locales)
diff --git a/stdio-common/tst-printf-bz25691.c b/stdio-common/tst-printf-bz25691.c
index 44844e71c3..e66242b58f 100644
--- a/stdio-common/tst-printf-bz25691.c
+++ b/stdio-common/tst-printf-bz25691.c
@@ -30,6 +30,8 @@ 
 static int
 do_test (void)
 {
+  setlocale(LC_CTYPE, "C.UTF-8");
+
   mtrace ();
 
   /* For 's' conversion specifier with 'l' modifier the array must be
diff --git a/wcsmbs/wcsmbsload.c b/wcsmbs/wcsmbsload.c
index 0f0f55f9ed..97de9afd25 100644
--- a/wcsmbs/wcsmbsload.c
+++ b/wcsmbs/wcsmbsload.c
@@ -33,10 +33,10 @@  static const struct __gconv_step to_wc =
   .__shlib_handle = NULL,
   .__modname = NULL,
   .__counter = INT_MAX,
-  .__from_name = (char *) "ANSI_X3.4-1968//TRANSLIT",
+  .__from_name = (char *) "POSIX",
   .__to_name = (char *) "INTERNAL",
-  .__fct = __gconv_transform_ascii_internal,
-  .__btowc_fct = __gconv_btwoc_ascii,
+  .__fct = __gconv_transform_posix_internal,
+  .__btowc_fct = __gconv_btwoc_posix,
   .__init_fct = NULL,
   .__end_fct = NULL,
   .__min_needed_from = 1,
@@ -53,8 +53,8 @@  static const struct __gconv_step to_mb =
   .__modname = NULL,
   .__counter = INT_MAX,
   .__from_name = (char *) "INTERNAL",
-  .__to_name = (char *) "ANSI_X3.4-1968//TRANSLIT",
-  .__fct = __gconv_transform_internal_ascii,
+  .__to_name = (char *) "POSIX",
+  .__fct = __gconv_transform_internal_posix,
   .__btowc_fct = NULL,
   .__init_fct = NULL,
   .__end_fct = NULL,
@@ -67,7 +67,9 @@  static const struct __gconv_step to_mb =
 };
 
 
-/* For the default locale we only have to handle ANSI_X3.4-1968.  */
+/* The default/"POSIX"/"C" locale is an 8-bit-clean mapping
+   with ANSI_X3.4-1968 in the first 128 characters;
+   we lift the remaining bytes by <UDF00>.  */
 const struct gconv_fcts __wcsmbs_gconv_fcts_c =
 {
   .towc = (struct __gconv_step *) &to_wc,